Rocker reinforcement for an electric vehicle

Abstract

The reinforced rocker assembly comprises a closed section stiffener located in a hollow volume formed between the rocker components, wherein the stiffener is assembled to a rocker component in transition regions between an upper horizontal wall and an upper flange of said rocker component and in transition regions between a lower horizontal wall and a lower flange of said rocker component, and wherein in said transition regions, the angles α and β formed between the flange and the stiffener branch extending outwardly of the rocker component are between 90 degrees and 180 degrees.

Description

Rocker reinforcement for an electric vehicle The present invention relates to the reinforcement of a rocker for an electric vehicle. Environmental concerns and regulations related to rising levels of carbon dioxide in the atmosphere and local air pollution levels have led to the rise of electric vehicles. Compared to traditional internal combustion engine vehicles, electric vehicles have smaller engines, no fuel tank, and no exhaust system. On the other hand, electric vehicles have a significant battery pack, which is not found in internal combustion engines. There is a large battery pack that needs to be protected in the case of an electric vehicle. Several types of vehicles can be produced on a single platform, including traditional internal combustion engine vehicles, without a battery pack. It is necessary to reinforce the side structure next to the battery. One essential structural element that protects the battery pack, especially in the event of side impacts, is the rocker assembly. The rocker assembly consists of an inner and outer rocker, each essentially U-shaped with an upper and lower flange that are assembled together to form a closed cross-section that creates a hollow volume along the bottom of the vehicle. In order to reinforce the rocker assembly, one possibility is to place one or more stiffeners within the hollow volume of the rocker assembly. Such stiffeners can have an open or closed cross-section. An open-section stiffener can be easily assembled by welding or mechanical assembly to the inner and outer rocker flanges and vertical walls. Such a welding process will naturally integrate itself into the vehicle assembly sequence, since in any case, even in the absence of a stiffener element, there is a welding step to secure the lower and upper flanges of the inner and outer rocker panels. On the other hand, a closed-section reinforcement will generally exhibit a better resistance to compressive loads resulting from an impact and will also have a better stiffness performance. However, such closed-section reinforcements cannot structurally have surfaces that allow them to be easily assembled on the inner and outer rocker flanges. Furthermore, to maximize the reinforcing effect, it is interesting to design a reinforcement with a cross-section that occupies as much space as possible in the hollow volume of the rocker assembly. Such a configuration, whereby a closed-section reinforcing element occupies a large space in the rocker assembly, creates the problem of efficient assembly of the reinforcement to the inner and / or outer rocker. One problem is the accessibility of assembly tools, such as welding tools. Another problem is the geometric tolerances required to secure a good assembly: the inner and outer rocker as well as the reinforcement are made of high-strength materials such as steel and are large pieces that span the entire length of the passenger compartment of the vehicle. For example, the well-known springback problems require that the dimensional tolerances of the parts before assembly make it difficult to fasten them all together. Another problem is the mechanical efficiency of the rocker and reinforcement assembly. In fact, a simple problem with the above-mentioned issues of assembly tool accessibility and geometric tolerances is to fasten the reinforcement to the inner and / or outer rocker only at the front and rear ends of the assembly, which are easily accessible. However, when doing this, the inner and outer booster and rocker will not cooperate optimally in the event of an impact.For example, in the case of a pole impact, which is a very local application of the assembly, the pole penetration will sequentially cause the outer rocker, the stiffener, and the inner rocker to bend. Since the stiffener is not attached to the inner and outer rocker along the length of the vehicle, the bent portion of the stiffener is not restrained from bending by the surrounding portions of the inner and outer rocker. As a result, the pole penetration will be greater than if the stiffener were secured to the inner and outer rocker along the length of the vehicle, and the subsequent pole penetration into the battery pack will be greater, possibly leading to damage to the battery itself. One of the objectives of the present invention is to overcome these challenges by providing a rocker assembly with a closed-section reinforcement that occupies a large volume of the hollow space formed by the rocker assembly. To this end, the present invention relates to a reinforced rocker assembly comprising a closed section reinforcement placed in a hollow volume formed between the rocker components, wherein the reinforcement is assembled to a rocker component in transition regions between an upper horizontal wall and an upper flange of said rocker component and in transition regions between a lower horizontal wall and a lower flange of said rocker component, and wherein in said transition regions, the angles α and β formed between the flange and the reinforcement branch extending outwardly of the rocker component are between 90 and 180 degrees. By means of the above invention, it is possible to form a rocker assembly with a closed section reinforcement that occupies the entire vertical space available in the hollow volume and can be assembled to a rocker piece throughout the entire assembly in a continuous or semi-continuous manner. The resulting rocker assembly has optimized mechanical resistance in the event of a lateral impact, thanks to the excellent mechanical resistance of the closed section reinforcements, the maximum use of the space available for such reinforcement and the good cooperation between the minimum rocker piece to which it is assembled and the reinforcement. With regard to other optional features of the rocker assembly according to the invention, considered alone or with regard to any possible technical combination: - The rocker part to which the amplifier is assembled is the internal rocker. - The rocker part to which the booster is assembled is the outer rocker. - The amplifier is made of one part. - The amplifier is made of at least two different parts that are assembled together to form the amplifier. - The amplifier is assembled by welding using a filler wire technology. - The amplifier is assembled by MAG welding. - The reinforcement is assembled using a discontinuous assembly connection in the form of a stitch. - The stitches are aligned between the upper and lower transition zones. - The sutures are deviated between the upper and lower transition zones. - The amplifier is further assembled to the inner vertical wall of the rocker. - The booster is further assembled to the outer vertical wall of the rocker. - For any given cross-section, the closed section of the reinforcement occupies a surface area at least greater than 80% of the total surface area defined by the void volume between the inner rocker and the outer rocker. - For any given cross-section, the maximum dimension of the reinforcement in the vertical direction is at least 75% of the maximum dimension in the vertical direction of the hollow volume, and the maximum dimension of the reinforcement in the transverse direction is at least 75% of the maximum dimension in the transverse direction of the hollow volume. The present invention further relates to a method for producing a rocker assembly as described above, comprising the following steps: - Presenting a rocker piece - Placing a closed section reinforcement relative to said rocker part in a pre-assembly position - Fastening the closed section reinforcement to the rocker piece by connecting it at least in the transition areas between the upper flange and the upper horizontal wall of the rocker piece and in the transition areas between the lower flange and the lower horizontal wall of the rocker piece - Fastening the assembled rocker piece and reinforcement to the remaining rocker piece so that a reinforced rocker assembly is formed. Thanks to the specific shape and configuration of the assembly points described above, between the transition areas of the rocker piece and the reinforcement element, the assembly tools necessary to secure the reinforcement to the rocker piece will have enough space to access the assembly point. One advantage of the process described above is the flexibility resulting from the fact that the closed section reinforcement assembly does not change the initial assembly process between the inner and outer rocker. This means that the inner and outer rocker assembly process can be performed regardless of the presence of a reinforcement. Thanks to this flexibility, vehicles with and without reinforcement can be produced on the same production line. For example, a vehicle platform consisting of an internal combustion engine vehicle and a battery electric vehicle can be assembled on the same platform, the former without a battery pack would not need a reinforcement in the rocker assembly, while the latter would benefit from the additional protection of the battery pack provided by a reinforced rocker assembly. Optionally, the booster and rocker assembly are assembled using a filler wire welding technology. Optionally, the booster and rocker assembly are assembled using MAG welding. Optionally, the assembly process described above can include more of the following steps: - Assembly of the inner vertical wall of the rocker to the reinforcement. - Assembly of the outer vertical wall of the rocker to the reinforcement. Other aspects and advantages of the invention will become apparent upon reading the following description, given by way of example, and with reference to the accompanying drawings, in which: - Figure 1 is a general perspective view of a vehicle according to the invention - Figure 2 is a side view of a vehicle according to the invention. - Figure 3 is an exploded view of a reinforced rocker assembly according to an embodiment of the present invention - Figures 4, 5 and 6 are cross-sectional views taken along axis II-II of Figure 2 of a rocker arm and a reinforcement according to various embodiments of the present invention. - Figure 7 is a perspective view of a rocker assembly and a booster according to an embodiment of the present invention. - Figures a8 and b8 are side views of a rocker assembly and a booster according to various embodiments of the present invention. - Figure 9 is a cross-section along axis II-II of Figure 2 of a reinforced rocker assembly according to an embodiment of the present invention. In the following description, the terms "top", "bottom", "front", "rear", "transverse" and "longitudinal" are defined according to the usual directions of a mounted vehicle. Specifically, the terms "top" and "bottom" are defined according to the height direction of the vehicle (or Z direction in Figure 2), the terms "front", "rear" and "longitudinal" are defined according to the front / rear direction of the vehicle (or L direction in Figure 2), and the term "transverse" is defined according to the width of the vehicle. Referring to Figures 1 and 2, a reinforced rocker assembly 3 is described for an electric or hybrid vehicle 1 (hereinafter referred to simply as a vehicle) having a battery pack 5 located under the floor panel. The reinforced rocker assembly 3 forms part of the side structure of the vehicle. It extends from the passenger compartment of the vehicle in the longitudinal direction. It can be a stand-alone assembly, as will be explained in the following embodiments, or integrated into larger parts, such as an inner and outer door ring each made of a single part that is molded from a custom welded piece. The side structure of a vehicle is designed to protect the occupants of the vehicle in the event of a side impact. Such a side impact is described in various standardized crash tests such as the European New Car Assessment Program (EuroNCAP) Pole Side Impact, in which the vehicle is struck in the side by a fixed pole with a relative initial velocity at the time of impact of 32 km / h. Another standardized side impact test is the EuroNCAP Advanced European Mobile Barrier Deformable Side Impact (AE-MDB), in which the vehicle is struck in the side by a standard 1400 kg barrier that spans part of the vehicle's length and moves at a speed of 60 km / h. In the case of a vehicle 1 having a battery pack 5 located under the floor panel, the side structure is more responsible for protecting the battery pack 5 from damage. Since the reinforced rocker assembly 3 is located at the same height as the battery pack 5, it will directly contribute to protecting the battery pack. Referring to Figures 3 and 9, the reinforced rocker assembly 3 is comprised of two rocker pieces 31, 39 which when assembled together form a hollow volume 35. The rocker piece 31 located closer to the interior of the vehicle is referred to as the inner rocker 31. The rocker piece 39 located closer to the exterior of the vehicle is referred to as the outer rocker 39. The reinforced rocker assembly 3 is reinforced with a closed section reinforcement 34 which occupies the hollow volume 35. It should be understood that the hollow volume 35 represents the volume formed between the rocker parts 31, 39. This volume does not include the assembly points between the rocker parts 31, 39. For example, this volume does not include the assembly points in the flanges. In fact, the flanges are assembled flat on top of each other and therefore do not include a significant volume between each other. For clarity, the invention will be described hereinafter using the inner rocker 31 as the rocker member to which the closed section reinforcement will be attached. However, it should be noted that the invention is entirely symmetrical between the inner rocker 31 and the outer rocker 39, both of which have a generally U-shaped cross-section with upper and lower flanges, both of which serve the same function of forming a hollow volume 35 together, and both of which serve the function of resisting lateral impacts, both individually and synergistically when assembled to form a reinforced rocker assembly. Referring to FIG. 4, the inner rocker 31 has a generally U-shaped cross-section comprising an upper horizontal wall 312, a lower horizontal wall 314 connected by a vertical wall 313. It should be noted that the walls 312, 313 and 314 are not necessarily completely straight and can comprise various sections, for example in the case of the lower wall 314 of FIG. 4 comprising two vertical sections ha314 and hb314 connected by a vertical section v314. Such a design can be useful for accommodating other components or for stiffening the component and making it more resistant to buckling. In FIG. 4, the lower wall 314 comprises several sections, but this is a specific embodiment that is not limiting. The other walls 312 and 313 can also include multiple such sections according to the constraints and design choices made for the particular application. An upper and lower flange 311 and 315 extend from the upper and lower horizontal walls 312 and 314, respectively. Said flanges are designed to assemble the inner rocker 31 to the facing flanges of the outer rocker 39, for example by spot welding them together at several locations along their length. The assembled configuration of the reinforced rocker assembly is shown in Figure 9, where the assembled facing flanges of the two rocker pieces 31, 39 are clearly visible. Referring to FIG. 9 , the closed section amplifier 34 , hereinafter simply referred to as amplifier 34 , occupies a volume portion of the hollow volume 35 . Figure 4 shows the inner rocker 31 and the reinforcement 34 in their assembled position, before the reinforced rocker assembly 3 is fully formed by further assembling the outer rocker 39 by securing the inner and outer rocker flanges together. The reinforcement occupies part of the volume formed by the walls 312, 313 and 314 and extends outwardly from this confined volume. The reinforcement 34 is assembled to the inner rocker 31 in the transition region between the upper flange 311 and the upper horizontal wall 312 and in the transition region between the lower flange 315 and the lower horizontal wall 314. Referring to Figure 4, in order to allow access by an assembly tool to the assembly region in the transition regions, the angles α and β defined by the flanges 311, 315 and the reinforcement branch 34 extending outwardly of the inner rocker are at least 90 degrees. In fact, if one of the angles α or β is less than 90 degrees, the access region that the assembly tool will need to perform the assembly will be very narrow, requiring the implementation of special measures and the use of special tools to perform the assembly. This will have a negative impact on assembly costs and productivity. The access region may even be too narrow for any existing or conceivable assembly tool, making assembly practically impossible. Also, one of the features of the present invention is to limit the angles α and β to a maximum value of 180 degrees.In fact, if the angle is greater than 180 degrees, the relative position of the reinforcing extension branch 34 and the flange 311 or 315 will make their assembly difficult, if not industrially impossible, because they will not easily overlap once assembled. To further illustrate the assembly between the inner rocker 31 and the reinforcement 34 in the upper transition region between the upper wall 312 and the upper flange 311, a zoom in on the assembly area is provided in Figure 4. The connection 316 formed by the assembly tool is used to better understand the invention. It should be noted that the specific shape and appearance of the connection 316 depicted is an illustration for illustrative purposes and does not limit the scope of the invention. In a particular embodiment, the assembly technology for producing the 316 connection is a welding operation that includes a filler wire, such as a MAG or MIG welding process that uses a wire to secure the parts together. Another type of filler wire welding technology can be the use of a welding head that includes a laser beam that melts the filler wire. Advantageously, by using a filler wire welding technology, it is possible to fill a gap that may exist between the inner rocker 31 and the reinforcement 34 in the assembly areas described above. In an industrial setting such a gap will often occur, particularly when using very high strength steels which are subject to springback issues and make it impossible to achieve very tight geometric tolerances in industrial parts. Advantageously, the use of a filler wire welding process will ensure industrial strength and repeatability of the assembly process over a wide range of geometric tolerances. It should also be noted that the described design of the assembly region between the inner rocker 31 and the reinforcement 34 is particularly advantageous for the use of filler wire welding technologies because it provides an assembly configuration that can be designed to create an open space around the connection 316 toward the interior of the volume defined by the inner rocker walls 312, 313, and 314.This in turn provides ample space for fumes from the welding operation to escape the 316 joint, thereby minimizing the risk of bubbles becoming trapped in the 306 joint. Trapped bubbles weaken the weld joint and are a known problem in filler wire welding, especially when used on zinc-coated parts due to the low boiling point of zinc. In a particular embodiment shown in FIG. 7 , FIG. a8 and FIG. b8 , the assembly connection 316 between the inner rocker 31 and the reinforcement 34 is not continuous along the length of the parts in the longitudinal direction. Instead, discontinuous stitches are formed that are distributed along the longitudinal direction. Advantageously, fastening the parts using discontinuous stitches will reduce assembly time, reduce wear on assembly tools, and reduce filler wire consumption when using a filler wire welding technology. It will also reduce the overall weight of the assembly thanks to the lower amount of filler wire melted in the part. It will also reduce the amount of heat affected zone that can cause weakness in the assembled parts. It will also reduce the risk of thermal distortion of the parts due to the heat input of the welding process and provide a final assembly with better geometric tolerances. Additionally, when filler wire welding is used, seam welding will also reduce the risk of blistering at the weld joint because metal fumes from the welding operation will have a greater chance to escape around the edges of the seams.Finally, even if the assembly connection between the inner rocker 31 and the reinforcement is not continuous, the fact that the seams are present along a large surface along the length of the parts still ensures a very good mechanical cooperation between the parts in the event of a side impact. The stitches described above that form the 316 assembly connection can be aligned between the stitches in the upper transfer zone and the lower transfer zone, as shown in Figure 8b, or they can be offset in the longitudinal direction as shown in Figure 8a. Advantageously, the use of a staggered configuration can help reduce the effect of thermal distortion caused by the heat input of the welding operation. In a particular embodiment, the reinforcement 34 can be assembled in other areas that convey areas in addition to the inner rocker 31, for example by securing the reinforcement 34 to the vertical wall 313 using an adhesive bond. For example, the adhesive can be applied before the reinforcement 34 is placed within the inner rocker 31. The adhesive can be applied to the outer surface of the closed cross-section of the reinforcement 34 or to the vertical wall 313 or to both surfaces. Advantageously, further securing the reinforcement 34 to the inner rocker 31 as described will further strengthen the bond between the two parts and thereby increase their positive engagement in the event of a side impact. Furthermore, this step of securing the reinforcement 34 to the inner rocker 31 in areas other than the transition areas can be performed prior to the step described above for assembling both parts in the transition areas. The advantage is that by doing so, both parts can be secured together in a secure manner, such that they will not move during their assembly in the transition areas. Figures 4, 5 and 6 show several different possible embodiments of the reinforcement 34. The reinforcements 34 of Figures 4 and 5 are both made from a single piece that can be produced, for example, by a roll forming operation followed by a welding operation to close the cross-section. The reinforcement of Figure 5 differs from Figure 4 in that there is a geometric change in the wall extending outwardly from the inner rocker 31 in the lower transition region that is not present in the reinforcement of Figure 4 (the reinforcement wall extending outwardly from the inner rocker in the lower transition region in Figure 4 is straight). The effect of such a geometric feature is to increase the angle β and thereby provide more space for the assembly tool to access the assembly area in order to make an assembly connection 316 in the lower transition region. The reinforcements 34 shown in Figures 4 and 5 also exhibit specific features to make them more resistant to the compressive load resulting from a lateral impact. In fact, the internal horizontal walls of said reinforcements extend in two distinct planes as shown in Figure 5: the upper internal horizontal wall extends along planes a341 and b341, the lower internal horizontal wall extends along planes a342 and b342. By providing such a reinforcement 34 with horizontal walls extending on at least two different planes, it is possible to design a reinforcement 34 that has a greater resistance to compressive loads and in particular a better resistance to buckling under compressive loads. The reinforcement 34 shown in Figure 6 is made up of two separate pieces, an inner reinforcement a34 and an outer reinforcement b34, which are assembled together, for example by MAG welding or laser welding, to form the reinforcement 34. The inner reinforcement a34 is made up, for example, by roll forming and welding. The outer reinforcement b34 is made up, for example, by cold stamping or hot stamping. By providing a reinforcement 34 made up of several different pieces assembled together, it is possible to optimize the use of materials in the different parts of the reinforcement 34. It is also possible to design a reinforcement 34 with a shape that cannot be achieved using only one piece. In the case of an amplifier made of at least two different parts assembled together, the geometric tolerances of the assembly will be a combination of the geometric tolerances of the various sub-parts constituting the amplifier 34 .As previously mentioned, the use of high strength steels with their associated springback problem can create high geometric tolerances and this effect is increased in the case of composite geometric tolerances for a reinforcement 34 comprising several sub-parts. In this case, the use of a filler wire welding technology as previously described is more advantageous in order to accommodate the distribution of geometric tolerances that will be encountered in an industrial mass production setup. In general, the invention can be implemented using any shape of closed section reinforcement 34, provided that the angles α and β are in the range of 90 degrees to 180 degrees. The shape, material and thickness of the reinforcement 34 will be designed by the designers to meet the specific constraints associated with its installation in the hollow volume 35 and the specific requirements associated with side impact and possibly other requirements such as body stiffness, front impact, rear impact, etc. Other constraints that must be considered include manufacturing costs and component weight, among other constraints. Once the inner rocker 31 and the reinforcement 34 are secured together, the outer rocker 39 is secured to the inner rocker 31 at their respective flange areas to form the reinforced rocker assembly 3. As previously noted, assembling the reinforcement 34 to the inner rocker 31 and then assembling this subassembly to the outer rocker 39 is one possible embodiment that has been described for the sake of simplicity. However, the invention can also be practiced by assembling the reinforcement 34 to the outer rocker 39 and then securing this subassembly to the inner rocker 31, both rocker components 31 and 39 having symmetrical roles. As previously described for the specific embodiment in which the reinforcement 34 and the inner rocker 31 are assembled in areas other than the transition areas, for example in the area of ​​the vertical wall 313, also in a specific embodiment the reinforcement 34 can be secured to the outer rocker 39, for example along the vertical wall of the outer rocker 39. For example, in the specific embodiment of FIG. 9, the reinforcement 34 can be secured to the outer rocker 39 in areas a39 and b39, where both parts are in contact with each other. This can be done for example by an adhesive connection. The adhesive can be applied for example to the reinforcement 34 or to the outer rocker 39 or to both parts. Advantageously, this further increases the bond between the reinforcement 34 and the outer rocker 39, thereby further enhancing the cooperation of the parts under compressive loads of a side impact, for example. The reinforced rocker assembly 3 described above is suitable for protecting a battery pack 5 in the event of a side impact. For example, in the case of a pole impact which is a very local application of the assembly, the pole penetration causes the outer rocker, the reinforcement and the inner rocker to bend sequentially. Since the reinforcement is well connected to at least one of the rocker components 31, 39 over a large length of the member in the longitudinal direction, the bent portion of the reinforcement 34 will be prevented from bending by the surrounding portions of the rocker component 31, 39 to which it is connected. As a result, the pole penetration will be less than if the reinforcement 34 were not connected to a rocker component 31, 39 along the length of the vehicle; thus the pole penetration into the battery pack will be less and the battery pack and battery cells will be protected. The reinforced rocker assembly 3 described above will also help to protect the occupants of the vehicle in the event of a side impact. It can also play an active role in the event of a front or rear impact by absorbing and transferring the impact load to other structural parts of the vehicle.This can further help increase the overall strength of the vehicle. In order to maximize the effect of the reinforcement 34 on the strength of the reinforced rocker assembly 3, it is advantageous to maximize the amount of space that the closed section of the reinforcement 34 occupies within the hollow volume 35. In a particular embodiment, for any given cross-section, the closed section of the reinforcement 34 occupies an area of ​​at least more than 80 percent of the total area defined by the hollow volume 35. In a particular embodiment, for any given cross-section, the maximum dimension of the reinforcement 34 in the height direction is at least 75 percent of the maximum dimension in the height direction of the hollow volume 35, and the maximum dimension of the reinforcement 34 in the transverse direction is at least 75 percent of the maximum dimension in the transverse direction of the hollow volume 35. In order to maximize the strength of the reinforced rocker assembly 3, it is advantageous to use very high strength steels to manufacture the rocker components 31, 39 and the reinforcement 34. In a particular embodiment, at least one of the rocker components 31, 39 is made of a pressure-hardened steel with a tensile strength greater than 950 MPa. According to one embodiment, the pressure-hardened steel composition in weight percent comprises: 0.06% ≤ C ≤ 0.1%, 1% ≤ Mn ≤ 2%, Si ≤ 0.5%, Al ≤ 0.1%, 0.02% ≤ Cr ≤ 0.1%, 0.02% ≤ Nb ≤ 0.1%, 0.0003% ≤ B ≤ 0.01%, N ≤ 0.01%, S ≤ 0.003%, P ≤ 0.020%, less than 0.1% Cu, Ni and Mo, residual iron and unavoidable impurities resulting from preparation. With this composition range, the yield strength of this part is between 700 and 950 MPa, the tensile strength is between 950 MPa and 1200 MPa, and the bending angle is above 75 degrees. For example, this part is made of Ductibor® 1000. In a particular embodiment, at least one of the rocker components 31, 39 is made of a pressure-hardening steel having a tensile strength greater than 1300 MPa. According to one embodiment, the composition of the steel includes, for example, in weight percent: 0.20% ≤ C ≤ 0.25%, 1.1% ≤ Mn ≤ 1.4%, 0.15% ≤ Si ≤ 0.35%, ≤ Cr ≤ 0.30%, 0.020% ≤ Ti ≤ 0.060%, 0.020% ≤ Al ≤ 0.060%, S ≤ 0.005%, P ≤ 0.025%, 0.002% ≤ B ≤ 0.004%, remaining iron and unavoidable impurities resulting from preparation. With this composition range, the tensile strength of at least one of the rocker components 31, 39 after hardening under pressure is between 1300 and 1650 MPa. For example, at least one of the rocker components 31, 39 is made of Usibor® 1500. In a particular embodiment, at least one of the rocker components 31, 39 is made of a pressure-hardening steel having a tensile strength greater than 1800 MPa. For example, the steel composition of the non-deformable section of the reinforced 36 includes, in weight percent: 0.24% ≤ C ≤ 0.38%, 0.40% ≤ Mn ≤ 3%, 0.10% ≤ Si ≤ 0.70%, 0.015% ≤ Al ≤ 0.070%, Cr ≤ 2%, 0.25% ≤ Ni ≤ 2%, 0.015% ≤ Ti ≤ 0.10%, Nb ≤ 0.060%, 0.0005% ≤ B ≤ 0.0040%, 0.003% ≤ N ≤ 0.010%, S ≤ 0.005%, P ≤ 0.025%, residual iron and unavoidable impurities resulting from preparation. With this combination range, the tensile strength of at least one of the rocker components 31, 39 after hardening under pressure is higher than 1800 MPa. For example, at least one of the rocker components 31, 39 is made of Usibor® 2000. In a particular embodiment, at least one of the rocker components 31, 39 or the reinforcement 34 is made of a fully martensitic steel with a tensile strength greater than 1100 MPa. For example, at least one of the rocker components 31, 39 or the reinforcement 34 is made of MartiNsite® 1100. In a particular embodiment, at least one of the rocker components 31, 39 or the reinforcement 34 is made of a fully martensitic steel with a tensile strength greater than 1200 MPa. For example, at least one of the rocker components 31, 39 or the reinforcement 34 is made of MartiNsite® 1200. In a particular embodiment, at least one of the rocker components 31, 39 or the reinforcement 34 is made of a fully martensitic steel with a tensile strength greater than 1300 MPa. For example, at least one of the rocker components 31, 39 or the reinforcement 34 is made of MartiNsite® 1300. In a particular embodiment, at least one of the rocker components 31, 39 or the reinforcement 34 is made of a fully martensitic steel with a tensile strength greater than 1500 MPa. For example, at least one of the rocker components 31, 39 or the reinforcement 34 is made of MartiNsite® 1500. In a particular embodiment, at least one of the rocker components 31, 39 or the reinforcement 34 is made of a fully martensitic steel with a tensile strength greater than 1700 MPa. For example, at least one of the rocker components 31, 39 or the reinforcement 34 is made of MartiNsite® 1700. In a particular embodiment, at least one of the rocker components 31 , 39 or the reinforcement 34 is coated with a metallic coating that provides corrosion protection, such as a zinc-based coating. In a particular embodiment, the thickness of the steel used to construct the rocker components 31, 39 and the reinforcement 34 is between 1.0 mm and 2.0 mm. The present invention further relates to a method for producing a reinforced rocker assembly 3 as described above, comprising the following steps: - Introducing the first component of the Rocker 31, 39 series - Placing a closed section reinforcement 34 relative to the first rocker part 31, 39 in a pre-assembly position - Fastening the reinforcement 34 to the first rocker component 31, 39 by connecting it at least in the transition areas between the upper flange and the upper horizontal wall of the first rocker component 31, 39 and in the transition areas between the lower flange and the lower horizontal wall of the first rocker component 31, 39 - Secure the resulting assembly between the first rocker component 31, 39 and the reinforcement 34 to the other rocker components 31, 39 to form a reinforced rocker assembly 3. Thanks to the specific shape and configuration of the assembly points described above, between the transition area of ​​the first rocker component 31, 39 and the reinforcement 34, the assembly tools necessary to secure the reinforcement 34 to the first rocker component 31, 39 will have sufficient space to access the assembly point. One advantage of the process described above is the flexibility resulting from the fact that the presence of the reinforcement 34 does not change the base assembly process between the first rocker components 31 and 39. This means that the same rocker base assembly process can be carried out regardless of the presence of a reinforcement 34. Thanks to this flexibility, vehicles with and without reinforcements can be produced on the same production line. For example, a vehicle platform comprising an internal combustion engine vehicle and a battery electric vehicle can be assembled on one platform, the former without a battery pack not requiring a reinforcement in the rocker assembly, while the latter will benefit from the additional protection of the battery pack provided by a reinforced rocker assembly 3. Optionally, the reinforcement 34 and the first rocker component 31, 39 are assembled by a filler wire welding technology. Optionally, the reinforcement 34 and the first rocker component 31, 39 are assembled by MAG welding. Optionally, the assembly described above between the reinforcement 34 and the first rocker component 31, 39 is accomplished using a discontinuous assembly connection 316, also known as stitches. Optionally, the stitches in the upper transition region and the lower transition region are aligned with each other. Optionally, the stitches in the upper transition region and the lower transition region are offset with each other. Optionally, the assembly process described above can also include the following steps: - Assembly of the inner vertical wall of the rocker to the reinforcement. - Assembly of the outer vertical wall of the rocker to the reinforcement.

Claims

Claims 1. A rocker assembly (3) comprising a closed section reinforcement (34) located in a hollow volume (35) formed between rocker components (31, 39), wherein the reinforcement (34) is assembled to a rocker component (31, 39) in regions of the assembly located in the transition regions between an upper horizontal wall and an upper flange of said rocker component (31, 39) and in the transition regions between a lower horizontal wall and a lower flange of said rocker component (31, 39), and wherein in said transition regions, the angles α and β formed between the upper and lower flanges and the respective parts of the reinforcement (34) extending outwardly of the rocker component assembly regions (31, 39) are comprised between 90° and 180°.

2. The reinforced rocker assembly (3) according to claim 1, wherein the rocker component to which the reinforcement is assembled is the inner rocker (31).

3. The reinforced rocker assembly (3) according to claim 1, wherein the rocker component to which the reinforcement is assembled is the outer rocker (39).

4. Reinforced rocker assembly (3) according to any one of claims 1 to 3, wherein the reinforcement (34) is made from a single part.

5. A reinforced rocker assembly (3) according to any one of claims 1 to 3 wherein the reinforcement (34) is made of at least two different pieces assembled together to form the reinforcement (34).

6. Reinforced rocker assembly (3) according to any one of claims 1 to 5, wherein the reinforcement (34) is assembled to the rocker component (31, 39) by welding using a filler wire welding technology.

7. Reinforced rocker assembly (3) according to any one of claims 1 to 6, wherein the reinforcement (34) is assembled to the rocker component (31, 39) by MAG welding.

8. A reinforced rocker assembly (3) according to any one of claims 1 to 7, wherein the reinforcement (34) is assembled to the rocker component (31, 39) using a suture-like discontinuous assembly connection (316).

9. The reinforced rocker assembly (3) according to claim 8, wherein the stitches of the upper and lower transition zones are aligned.

10. The reinforced rocker assembly (3) according to claim 8, wherein the stitches of the upper and lower transition zones have a deflection.

11. Reinforced rocker assembly (3) according to any one of claims 1 to 10, wherein the reinforcement (34) is additionally assembled to the vertical wall of the inner rocker (31).

12. Reinforced rocker assembly (3) according to any one of claims 1 to 10, wherein the reinforcement (34) is additionally assembled to the vertical wall of the outer rocker (31).

13. Reinforced rocker assembly (3) according to any one of claims 1 to 12, wherein for any given cross-sectional area, the reinforcing closed portion (34) occupies a surface area of ​​at least more than 80% of the total surface area defined by the void volume (35) at the given cross-sectional area.

14. A reinforced rocker assembly (3) according to any one of claims 1 to 12, wherein for any given cross-sectional area, the maximum dimension of the reinforcement (34) in the height direction is at least 75% of the maximum dimension in the height direction of the hollow volume (35) and the maximum dimension of the reinforcement (34) in the transverse direction is at least 75% of the maximum dimension in the transverse direction of the hollow volume (35).

15. An assembly process for producing a rocker assembly (3) according to any one of claims 1 to 14, comprising the steps of: - providing a first rocker component (31, 39) - placing a closed section reinforcement (34) relative to said first component (31, 39) in a pre-assembly position - securing the reinforcement (34) to the first rocker component (31, 39) by connecting it at least in the transition areas between the upper flange and the upper horizontal wall of the first rocker component (31, 39) and in the transition areas between the lower flange and the lower horizontal wall of the rocker component (31, 39) - securing the assembled first rocker component (31, 39) and the reinforcement (34) to the remaining rocker component (31, 39) so as to form a reinforced rocker assembly (3).

16. The assembly process according to claim 15, wherein the reinforcement (34) and the first rocker component (31, 39) are assembled using a filler wire welding technology.

17. The assembly process according to claim 15 or 16, wherein the reinforcement (34) and the first rocker component (31, 39) are assembled using MAG welding.

18. The assembly process according to any one of claims 15 to 17, further comprising the step of assembling the vertical wall of the inner rocker (31) to the reinforcement (34).

19. The assembly process according to any one of claims 15 to 18, further comprising the step of assembling the outer rocker vertical wall (39) to the reinforcement (34).