A unitary roof ring of a vehicle frame

Abstract

This disclosure relates to methods for manufacturing a unit roof ring (100) for a vehicle frame. The method comprises providing several blanks (1, 2, 3, 4), joining them together to form a combined piece (5), and deforming that combined piece (5) to form the unit roof ring (100). The unit roof ring (100) includes two longitudinal rail sections (10, 20), each connected to a front crossmember (30) and a rear crossmember (40), thus forming a substantially closed ring. This disclosure also relates to unit roof rings that can be obtained by these methods.

Description

A unitary roof ring of a vehicle frame

[0001] This application claims the benefit of European patent application no. 22 383 193.4 filed on December 7, 2022.

[0002] This disclosure relates to unitary roof rings for vehicles and manufacturing processes for unitary roof rings for vehicles. Background

[0003] Vehicles, such as automobiles, incorporate a structural frame designed to withstand all the loads to which the vehicle may be subjected during its service life. The structural frame is also designed to resist and absorb impacts, in the event of, for example, collisions with other cars, obstacles, or pedestrians.

[0004] The structural skeleton of a vehicle, for example a car, may include, in this sense, for example, bumpers, pillars (A-pillar, B-pillar, C-pillar, D-pillar), side impact beams, oscillators or footrests, hinge pillars and shock absorbers.

[0005] Press hardening, also known as hot die forming and tempering (HFDQ), typically uses boron steel sheets to create stamped components with ultra-high-strength steel (UHSS) properties, with tensile strengths of, for example, 1500 MPa or 2000 MPa or even higher. The increased strength allows for the use of thinner gauge material, resulting in lower weight compared to conventionally cold-formed mild steel components. Throughout this disclosure, UHSS may be considered to be steel having a maximum tensile strength of 1000 MPa or higher, particularly after a press hardening process.

[0006] In an HFDQ process, a sheet to be hot-formed can be heated to a predetermined temperature, for example, the austenitizing temperature or higher (and, in particular, between Ac3 and the evaporation temperature of, for example, a coating on the sheet). A furnace system can be used for this purpose. Depending on the specific requirements, a furnace system can be supplemented with additional heaters, for example, induction or infrared heaters. Heating the sheet reduces its strength and increases its deformability, thus facilitating the hot stamping process.

[0007] Several ultra-high-strength steels (UHSS) are known for hot stamping and hardening. The hot-formed shape can be made, for example, from boron steel, coated or uncoated, such as Usibor® (22MnB5), commercially available from ArcelorMittal.

[0008] Typical vehicle components that can be manufactured using the HFDQ process include: door beams, bumper beams, side crossmembers / bars, A / B pillar reinforcements, front and rear rails, seat crossmembers, and rear rails.

[0009] Hot forming of boron steels is becoming increasingly popular in the automotive industry due to their excellent strength and formability. Many structural components that were traditionally cold-formed from mild steel are therefore being replaced by hot-formed equivalents that offer a significant increase in strength. This allows for reductions in material thickness (and therefore weight) while maintaining the same strength.

[0010] To improve ductility and energy absorption in specific areas of a component, it is known to introduce softer regions within the component. This improves ductility locally while maintaining the required high overall strength. By locally adapting the microstructure and mechanical properties of certain structural components so that they comprise regions with very high strength (very hard regions), i.e., regions with high tensile strength and high yield strength, and regions with increased ductility (softer regions), i.e., regions with lower tensile strength, lower yield strength, and increased elongation before fracture, it may be possible to improve their overall energy absorption, maintain their structural integrity during a collision, and also reduce their overall weight.These soft zones can also advantageously change the kinematic behavior in the event of a component collapsing under an impact.

[0011] Known methods for creating regions of increased ductility ("soft zones") in vehicle structural components include the provision of tools comprising a pair of complementary upper and lower die units, each unit having separate die elements (steel blocks). A blank to be hot-formed is preheated to a predetermined temperature, e.g., the austenitizing temperature or higher, e.g., by a furnace system to reduce resistance, i.e., to facilitate the hot stamping process.

[0012] Die elements can be designed to operate at different temperatures, to have different cooling rates in different areas of the part being formed during the quenching process, and thus result in different material properties in the final product. For example, softer areas will generally have lower tensile strength and a lower yield strength, but allow for greater elongation before fracture. For instance, a die element can be quenched to harden the corresponding area of ​​the component being manufactured at high cooling rates, thereby rapidly reducing the component's temperature and obtaining a hard martensitic microstructure.Another adjacent die element can be heated to ensure that the corresponding part of the manufactured component cools at a slower rate, resulting in a softer microstructure that includes, for example, bainite, ferrite, and / or pearlite. Such an area of ​​the component may remain at higher temperatures than the rest of the component as it leaves the die.

[0013] Other procedures for obtaining hot-stamped components with areas of different mechanical properties include, for example, customized or differential heating before stamping and local heat treatments after a stamping process to change the local microstructure and obtain different mechanical properties. Still other possibilities include the use of patch-type and custom welded (TWB) types combining different thicknesses and / or materials in the types.

[0014] UHSS can exhibit tensile strengths up to 1500 MPa, or even 2000 MPa or more, particularly after a press-hardening operation. Once hardened, UHSS can have a martensitic microstructure. This microstructure allows for increased maximum tensile strength and yield strength per unit weight.

[0015] In addition to the ultra-high-strength steels mentioned above, more ductile steels can also be used in structural skeleton components that require energy absorption. These steels can be used in hot stamping processes, but they will not develop a martensitic microstructure. Ductibor® 1000 is an example of a suitable more ductile steel.

[0016] The upper frame of a vehicle's structural skeleton can be formed by connecting multiple structural parts. These structural parts form a roof ring, which is one of the structures that plays a role in protecting the vehicle in impact events. A vehicle's roof ring generally comprises four beams: two longitudinal rail sections, commonly known as roof rails, and front and rear crossmembers, commonly known as front and rear headers. The roof rails are located between the A-pillar and the C-pillar of the vehicle. The front header is located between the A-pillars, and the rear header between the C-pillars. In the event of an accident, the roof ring plays a crucial role in ensuring the vehicle's integrity.

[0017] The four beams comprising the roof ring can have different thicknesses and can be manufactured in different ways. The roof rails and front headrest are parts with high desired rigidity, generally achieved by hot stamping ("press hardening"), which aims to limit intrusion in the event of an impact while maintaining a relatively low weight. The rear headrest is typically made of a material suitable for cold stamping. After these four beams are manufactured, they are generally welded together when assembled with the rest of the vehicle frame or "body blank."

[0018] One problem that has been encountered is that the various welding points and seams can create vulnerable areas in a collision. Other aspects to consider are weight, manufacturability, time required to build the vehicle, and cost. US patent 2007 / 0228777 A1 discloses a roof structure for a vehicle that includes a custom-welded format. US patent 2021 / 0221439 A1 discloses a method for manufacturing a unitary body-side structural frame for a vehicle comprising providing a plurality of formats, joining the formats together to form a composite format that forms one or more overlapping regions formed by partially overlapping two formats, and deforming the composite format.

[0019] This disclosure provides examples of systems and procedures that provide improvements over prior art roof structures. Brief explanation

[0020] In a first aspect, a method for manufacturing a unitary roof ring of the vehicle structural frame is provided. The method comprises providing a plurality of formats, joining the formats to form a combined format, deforming the combined format to form a unitary roof ring, wherein the unitary roof ring includes two longitudinal rail portions each connected to a front crossmember and a rear crossmember to form a substantially closed ring conformation.

[0021] By joining the forms together to create a combined form and then deforming the combined form, a lightweight and strong roof ring is produced in fewer stages. Joining the forms together before deforming allows for the fabrication of a roof ring with areas that are unaffected by heat or less affected by heat, as welding operations after forming are reduced. These less heat-affected areas reduce the risk of cracking in the upper frame of the structural skeleton in the event of a collision. This can lead to increased strength in the roof ring while reducing the thickness of the forms and minimizing weak points in the final ring. Therefore, collision performance can be improved while achieving a reduction in the mass of the vehicle's upper frame, which may allow for a reduction in the thickness of neighboring roof ring components.

[0022] In some examples, the plurality of formats comprises one front crossbeam format, two longitudinal beam formats, and one rear crossbeam format. In some examples, the plurality of formats may be made of ultra-high-strength steel (UHSS), and one or more of the formats may be specifically made of boron steel.

[0023] In some examples, formats of different thicknesses and / or material qualities can be used to meet specific requirements for strength, anti-intrusion and energy absorption and to optimize weight.

[0024] In some examples, joining formats involves forming one or more overlapping regions by partially overlapping the formats with each other. In this disclosure, two partially overlapping formats means that only a portion of the two formats overlaps.

[0025] One or more overlapping regions may be arranged to counteract the reduction of material and therefore strength that may occur in some sections of the unit roof ring compared to solutions in which the structural components are formed first and then joined together to form the upper structural frame.

[0026] Alternatively or additionally, the overlay can be placed in locations where high loads are expected, for example by placing patch formats within the formats.

[0027] Throughout this disclosure, the front and rear crossbeam formats may be considered formats that are subsequently deformed to form the front and rear crossmembers of the roof ring. Similarly, the longitudinal beam formats may be considered formats that are subsequently deformed to form the longitudinal rail portions of the roof ring.

[0028] The roof rails and the front and rear headrests of the vehicle are structural members of the upper structural frame of the vehicle. In some examples, the longitudinal rail portions included in the unit roof ring may be the outer roof rail members of the vehicle frame, and the front crossmember and rear crossmember included in the unit roof ring may be the front and rear headrests of the vehicle frame.

[0029] The unit roof ring can define the upper structural frame of a vehicle.

[0030] In some examples, the deformation of the combined form to create a unitary roof ring for a vehicle frame comprises hot stamping the combined form. Hot stamping is a process that allows the appropriate deformation of ultra-high-strength steel to form the complex structure resulting from the unitary roof ring.

[0031] In some examples, deforming the combined form can be performed in a single operation. Deforming the combined form in a single operation can result in improved manufacturing efficiency for a vehicle frame roof ring.

[0032] In an additional aspect, a unitary roof ring is provided which is obtained by a procedure in accordance with any of the examples described herein. Brief description of the drawings

[0033] Non-limiting examples of this disclosure will be described below, with reference to the accompanying figures, in which: Figure 1 shows an example of a unitary roof ring of a vehicle frame; Figure 2 shows an example of a plurality of formats before they are joined together to form a combined format; Figure 3 shows an example of a schematic view of a combined format made up of four joined formats; Figure 4 shows an example of a combined format comprising patch formats; Figure 5 shows an example of a combined format comprising five joined formats; Figure 6 shows an example of a unit roof ring after deforming the combined format; Figure 7 shows an example of an enlarged view of joined formats after deforming into a unit roof ring of a vehicle frame; Figure 8 shows an example of a front view of a unitary roof ring of a vehicle frame; and Figure 9 is a flowchart of a manufacturing procedure for a unit roof ring of a vehicle frame.

[0034] The figures refer to example implementations and may only be used as an aid to understanding the claimed subject matter, not to limit it in any way. Detailed description of examples

[0035] In these figures, the same reference signs have been used to designate matching elements.

[0036] Figure 1 schematically represents a unitary roof ring 100 of a vehicle frame according to an example in this disclosure. The unitary roof ring 100 includes two longitudinal rail portions 10, 20 each connected to a front crossmember 30 and a rear crossmember 40 to form a substantially closed ring configuration.

[0037] In some examples, the Unit Roof Ring 100 can be installed on the upper frame of the vehicle frame and can define a vehicle's upper structural frame. The Unit Roof Ring can be attached to other parts of the vehicle frame, such as the A-pillars, C-pillars, and roof panels.

[0038] The unit roof ring 100 can be made from a plurality of formats in a single forming process. As illustrated schematically in Figure 2, the unit roof ring 100 can be made from four formats: a first format 1, a second format 2, a third format 3, and a fourth format 4, wherein the first and second formats 1 and 2 can be longitudinal beam formats 1 and 2, and the third and fourth formats 3 and 4 can be transverse beam formats 3 and 4. The third format 3 can be a front transverse beam format 3, and the fourth format 4 can be a rear transverse beam format 4. The formats can be joined together to form a combined format. Longitudinal beam formats 1, 2 can be joined to the front cross beam format 3 and the rear cross beam format 4. Therefore, a combined format 5 can be formed which includes the four formats 1, 2, 3, 4, as shown in figure 3.

[0039] At a later stage, the combined form 5 can be deformed. In particular, the combined form can be heated above an austenitizing temperature, for example, around 90–920 °C in a furnace or alternative heating system. Subsequently, the combined form can be deformed and hardened in a pressing apparatus. In particular, rapid cooling above a critical cooling rate of the combined form can achieve a martensitic microstructure and high ultimate tensile strength and yield strength.

[0040] In some examples, the formats can be joined together to form one or more overlapping regions 6 created by partially overlapping the formats. That is, one format is placed only partially on top of another format, and then the formats are joined together. Therefore, an overlapping region acquires an increased thickness compared to the rest of the formats. This increase in thickness can be used to adapt the mechanical properties as needed and provide local reinforcements, for example, in areas where increased strength and / or stiffness is required.

[0041] In some examples, overlap regions 6 can be formed at or near a joint or transition point of the front crossmember 30 with one of the longitudinal rail parts 10, 20. When the different components are combined into a unit roof ring 100 by deforming a single format, these joint points have less material than they would have when the component is manufactured separately and then welded together. By providing overlap regions 6 at or near these joint points, additional material can be added, thus maintaining the mechanical behavior and kinematic properties of the roof ring 100. In other examples, the combined format could be formed by edge-to-edge welding of formats (such as a custom-welded format), or the combined format could be formed by using overlapping formats in specific regions and edge-to-edge welding in other regions.

[0042] In some examples, an overlap region 6 may be formed substantially within the front member 30. That is, in these examples, the formats that constitute the longitudinal beams overlap with the format(s) that constitute the front member 30. In the resulting product, the overlap may be located completely or almost completely within the front member 30 of the resulting unit roof ring. In other examples, overlap regions 6 may be formed at each of the joining points or transitions of the front and rear cross members 30, 40 with the two longitudinal rail portions 10, 20. The overlap may be achieved by laser welding, arc welding, or spot welding.

[0043] In some examples, as shown in Figure 3, joining the formats comprises joining a first end of a first longitudinal beam format 1 to a first end of a front cross beam format 3 and a second end of the first longitudinal beam format 1 to a first end of a rear cross beam format 4, and joining a first end of a second longitudinal beam format 2 to a second end of a front cross beam format 3 and a second end of a second longitudinal beam format 2 to a second end of a rear cross beam format. The formats can be welded together, for example, by laser welding or spot welding. The region 6 where the formats are joined can be seen in Figure 3.

[0044] In some examples, joining the formats to form a combined format 5 comprises giving the combined format 5 a substantially rectangular (annular) shape.

[0045] In some examples, longitudinal beam formats 1, 2 can be joined to transverse beam formats 3, 4 on the outer / top side of the roof ring. In other examples, longitudinal beam formats 1, 2 can be joined to transverse beam formats 3, 4 on the inner / bottom side of the roof ring.

[0046] In some examples, the overlap region 6 may have a length L1 corresponding to a width of the longitudinal rail portion 10, 20 and may have a width W1 of at least 5 cm. In some examples, the overlap regions 6 may be formed at each of the joining points of the front and rear crossmembers 30, 40 with the two longitudinal rail portions 10, 20. The appropriate dimensions of the overlap region 6 may be chosen taking into account weldability, strength, and stiffness requirements. A larger overlap region 6 means an increase in thickness over a larger area and therefore an increase in strength and stiffness locally at the roof ring 100.

[0047] In other examples, the plurality of formats can be formed by a plurality of formats or sub-formats, for example, of different thicknesses and / or different materials. In these examples, the plurality of formats forming the longitudinal beam formats and / or the transverse beam formats can be custom-welded (TWB) formats. A TWB can be formed by joining the sub-formats by edge-to-edge welding, where the welding can include laser welding. In other examples, the plurality of formats forming the longitudinal beam formats 1, 2 and / or the transverse beam formats 3, 4 can be joined by forming one or more overlapping regions 6, which are formed by partially overlapping the formats with each other. In these cases, any laser welding, arc welding, or spot welding method can be used.

[0048] As illustrated schematically in Figure 4, in some examples a patch format 7 can be joined to at least one of the plurality of formats that can form the combined format 5. A patch format may be considered herein as a format that completely overlaps another format; that is, a patch format can be entirely contained within the perimeter of another format. The patch format can be joined to the other format by welding, for example, spot welding or remote laser welding. The resulting combination of the "basic" format and the patch format may sometimes be referred to as a "patch format."

[0049] Patch format 7 can be substantially added to a central portion of one of the formats. A patch format 7 can be added as reinforcement to increase the strength of a specific area of ​​the combined format 5. A patch format 7 can be added to areas of the roof ring where additional strength may be required, i.e., where high loads are expected. In some examples, a patch format 7 can be arranged within the front and / or rear crossbeam formats 3, 4. Patch format 7 can be substantially arranged to a central portion of the front and / or rear crossbeam formats 3, 4. A patch format 7 can also be arranged to the longitudinal beam formats 1, 2, for example, in the area above the vehicle's B-pillar. Patch format 7 can be substantially arranged to a central portion of the longitudinal beam formats 1, 2.

[0050] Patch formats 7 can be joined to longitudinal beam formats 1, 2 and / or transverse beam formats 3, 4 by overlapping one format with the other and using spot welding. In other examples, alternative welding techniques, such as laser welding or arc welding, can be used.

[0051] As illustrated schematically in Figure 5, a unit roof ring may include one or more additional crossbeams located between the front and rear crossbeams. In some examples, such as the example in Figure 5, the unit roof ring 100 may be made from a combined format consisting of five formats. In addition to the formats illustrated, for example, in Figures 2 and 3, the combined format 5 may comprise a center crossbeam format 8 located between the front crossbeam format 3 and the rear crossbeam format 4, and extending transversely from the longitudinal beam format 1 to the longitudinal beam format 2. The center crossbeam format 8 may be joined to the longitudinal beam formats 1 and 2, for example, by partially overlapping the formats.A center crossmember in the unit roof ring can provide a superior structural frame for a vehicle with enhanced crash performance and reduced weight.

[0052] In the example in Figure 5, the overlap region 6 formed by partially overlapping the front and rear crossbeam formats 3, 4 with the longitudinal beam formats 1, 2 can have a width W1 of at least 50% of the width of the front and rear crossbeam formats 3, 4. In this example, a larger section of the longitudinal beam formats 1, 2 can be overlapped with the crossbeam profiles 3, 4 compared to the example in Figure 3. In this case, the overlap region is not located entirely within the longitudinal beams but occupies part of the longitudinal beam as well as part of the rear crossbeam. Increased stiffness can be provided over a wider area of ​​the unit roof ring, and greater loads can be resisted by increasing the size of the overlap region 6.

[0053] In this particular example, a patch format 7 can be substantially placed in a central portion of the front crossbeam format 3. In other examples, a patch format 7 can also be added to the longitudinal beam formats 1 and 2 to further reinforce specific areas of these formats. In some examples, a patch format 7 can be substantially placed in a central portion of the longitudinal beam formats 1 and 2, overlapping with a portion of the central crossbeam format 8.

[0054] In some examples, the plurality of formats that make up the combined format 5 can be made of different materials. In some examples, formats 1, 2, 3, and 4 can be made of ultra-high-strength steels (UHSS). Boron steel, for example 22MnB5, or other steel compositions mentioned or referred to above may be suitable UHSS. These formats, for example, boron steel formats, may comprise a silicon-aluminum coating or a zinc coating.

[0055] Usibor® 1500P is an example of a 22MnB5 steel. The composition of Usibor® is summarized below in weight percentages (the remainder is iron (Fe) and impurities): Maximum Carbon (C) (%): 0.25 Maximum Silicon (Si) (%): 0.4 Maximum Manganese (Mn) (%): 1.4 Phosphorus (P) maximum (%): 0.03 Sulfur (S) maximum (%) : 0.01 Aluminum (Al) (%) : 0.0 - 0.1 Maximum Titanium (Ti) (%): 0.05 Niobium (Nb) maximum (%) : 0.01 Maximum Copper (Cu) (%): 0. 20 Boron (B) maximum (%) : 0.005 Chromium (Cr) maximum (%) : 0.35

[0056] Usibor® 1500P can have a yield strength of, for example, 1100 MPa and a maximum tensile strength of 1500 MPa.

[0057] Usibor® 2000 is another boron steel with even greater strength. The yield strength of Usibor® 2000 can be 1400 MPa or more, and the ultimate tensile strength can exceed 1800 MPa. The composition of Usibor® 2000 is summarized below in weight percentages (the remainder is iron (Fe) and impurities): Maximum Carbon (C) (%): 0.36 Maximum Silicon (Si) (%): 0.8 Maximum Manganese (Mn) (%): 0.8 Phosphorus (P) maximum (%): 0.03 Sulfur (S) maximum (%) : 0.01 Aluminum (Al) (%) : 0.0.- 0.06 Maximum Titanium (Ti) (%): 0.07 Niobium (Nb) maximum (%) : 0.07 Maximum Copper (Cu) (%): 0. 20 Boron (B) maximum (%) : 0.005 Chromium (Cr) maximum (%) : 0.50 Molybdenum (Mb) maximum (%) : 0.50

[0058] The plurality of formats that make up the combined format 5 may comprise different materials and / or thicknesses. For example, Usibor® formats (e.g., Usibor® 1500 and / or Usibor® 2000) may be used in the formats that make up the combined format 5. The use of such materials in hot forming processes followed by tempering results in a predominantly martensitic structure due to the Usibor®. One or more of the formats may be made of a different material, e.g., Ductibor® 1000.

[0059] Ductibor® 1000 is another material used in hot stamping to increase elongation compared to Usibor® 1500 and Usibor® 2000. The yield strength of Ductibor® 1000 can be 800 MPa or more, and the ultimate tensile strength is 1000 MPa or more. The composition of Ductibor® 1000 is summarized below in weight percentages (the remainder is iron (Fe) and impurities): Maximum Carbon (C) (%): 0.10 Maximum Silicon (Si) (%): 0.6 Maximum Manganese (Mn) (%): 1.8 Phosphorus (P) maximum (%): 0.03 Sulfur (S) maximum (%) : 0.01 Aluminum (Al) (%) : 0.0 - 0.1 Maximum Titanium (Ti) (%): 0.05 Niobium (Nb) maximum (%): 0.10 Maximum Copper (Cu) (%): 0. 20 Boron (B) maximum (%) : 0.005 Chromium (Cr) maximum (%): 0.20

[0060] In some examples, the unit roof ring 100 may comprise areas with different maximum tensile strength according to any of the examples described herein. In some of these examples, different materials may be used in the combined format.

[0061] In some of these examples, areas with different maximum tensile strength may have a different microstructure.

[0062] Different microstructures can be created in a hot-formed roof ring. These different microstructures can be created by heating a combined form 5 above the austenitizing temperature and then controlling the cooling of the combined form 5 during forming it to form a roof ring 100 of a vehicle frame. The cooling of different areas of the combined form 5 can be controlled by providing heaters to areas of the forming tool. Accordingly, the unit roof ring 100 comprises areas with a predominantly martensitic structure and areas comprising ferrite, pearlite, or bainite, or a mixture thereof.Alternatively, a different microstructure can be created by partially heating, for example using a laser beam, a portion of the pressure-hardened unit roof ring to change the predominantly martensitic structure to one containing ferrite and / or pearlite and / or bainite and / or tempered martensite and a mixture thereof. The tensile strength of the predominantly martensitic structure can be above 1400 MPa and, specifically, above 1500 MPa.

[0063] Therefore, the unit roof ring 100 can be made of a material that can be effective in absorbing energy during an impact. In some examples, the longitudinal beam formats 1, 2 can be made of at least ultra-high-strength steel.

[0064] The thickness of longitudinal rail parts 10 and 20 can be 0.5–2.5 mm, specifically 1–1.8 mm. Longitudinal rail parts 10 can have a maximum tensile strength of 100–2000 MPa, specifically 150–2000 MPa. Longitudinal rail parts 10 and 20 can be the outer roof rail parts of the vehicle's upper structural frame.

[0065] In some examples, crossbeam formats 3, 4 can be made from at least one ultra-high strength steel.

[0066] The thickness of crossbars 30, 40 can be 0.5 - 2.5 mm, specifically 1 - 1.8 mm. An overlap region can have a thickness of 2 - 5 mm, specifically 2 - 3.8 mm.

[0067] The front and rear crossmembers 30, 40 may have a maximum tensile strength of 100-2000 MPa, specifically 150-2000 MPa. The front and rear crossmembers 10, 20 may be the front and rear end members of the vehicle's upper structural frame.

[0068] In some examples, the thickness of the front and rear crossmembers 30, 40 may be less than the thickness of the longitudinal rails 10, 20. In other examples, the thickness of the front and rear crossmembers 30, 40 may be equal to the thickness of the longitudinal rails 10, 20.

[0069] In some examples, joining the formats together involves welding them together. In some examples, the formats can be welded by spot welding and / or laser welding. In some examples, the combined format formed by joining the formats may be a custom-welded format. Joining the formats before deformation can facilitate the joining process because the formats are substantially flat at the time of joining. Welding the formats before the deformation process by spot welding and / or laser welding can be efficient and accurate.

[0070] Figure 6 schematically illustrates an example of formats joined after deformation. In this example, longitudinal beam formats 1, 2 can be joined to transverse beam formats 3, 4 by overlapping one format with the other and using spot welding before deformation. Figure 7 shows an enlarged view of the overlap region 6 of the joining points of the front crossmember 30 with the longitudinal rail portion 10. In other examples, joining the formats together may involve forming one or more overlap regions 6 by partially overlapping longitudinal beam formats 1, 2 with transverse beam formats 3, 4 by laser or spot welding.

[0071] Joining the sections can result in seams or weld points, critical areas that can easily rupture in the event of a traffic accident. Deforming after joining can ensure that there are no seams or weld points between the sections, providing a unitary 100 rear ring that is more impact-resistant than other structural upper frames where the structural components are formed first and then joined. The hazards caused by these seams or weld points are eliminated in the unitary 100 roof ring, thereby reducing the risk of cracking in the unitary 100 roof ring in the event of an accident. Furthermore, a unitary 100 roof ring can reduce the time required to build a vehicle and can allow for a reduction in the thickness of neighboring components of the 100 roof ring without compromising the thickness of its structural elements.

[0072] In some examples, deforming the combined format 5 to form the unit roof ring 100 may comprise hot forming or hot stamping the combined format 5. Figure 8 shows a schematic front view of a hot-formed unit roof ring 100.

[0073] In some examples, hot forming may comprise heating the combined form 5 above the austenitizing temperature and then forming the combined form 5 to create the unit roof ring 100. In some examples, the forming may comprise two or more forming stages. These forming stages may comprise, for example, shaping, trimming, or cutting and may be performed on a single multi-stage press. Examples of multi-stage presses are known from, for example, US 9,492,859 B2 and WO 2016142367 A1.

[0074] Deforming may include hot forming, i.e., heating the combined form 5 in a furnace, possibly above an austenitizing temperature, specifically above Ac3. After furnace heating, the combined form 5 may be transferred to a press where it is deformed to obtain the final shape of the unit roof ring 100. During and immediately after forming, quenching may be carried out. In particular, quenching may include cooling above a critical cooling rate so as to obtain a martensitic microstructure. In some instances, quenching may be avoided on selected portions of the roof ring.

[0075] In some examples, the deformation is carried out in a single operation. Deforming the combined format 5 can provide a unitary roof ring 100 that includes two longitudinal rail parts 10, 20 each connected to a front crossmember 30 and a rear crossmember 40 to form a substantially closed ring conformation.

[0076] In some examples, a roof ring 100 having substantially a ring-like shape comprising a front crossmember 30, a rear crossmember 40, a first longitudinal rail part 10 and a second longitudinal rail part 20 can be made by deforming a single format.

[0077] The unit roof ring 100 of this disclosure may have improved crash resistance and can be produced with fewer processes. Therefore, crash performance can be improved while reducing the mass of the vehicle's structural frame and the complexity of construction.

[0078] Figure 9 represents a flow diagram of a procedure for manufacturing a unitary roof ring of a vehicle frame 200. The procedure comprises providing a plurality of formats 201; joining the formats together to form a combined format 202; deforming the combined format to form a unitary roof ring 203.

[0079] In some examples, providing a plurality of formats 201 may comprise providing two longitudinal beam formats 1, 2, one front cross beam format 3, and one rear cross beam format 4. In some examples, the plurality of formats forming the combined format 5 may be made of different materials. In some examples, the longitudinal beam formats 1, 2 and the front and rear cross beam formats 3, 4 may be made of ultra-high-strength steel.

[0080] In some examples, joining the formats together to form a combined format 202 may involve forming one or more overlap regions 6 by partially overlapping the formats. The overlap region 6 may be formed at or near a joining or transition point of the front crossmember 30 with one of the longitudinal rail parts 10, 20. Overlap regions 6 may be formed at each of the joining points of the front and rear crossmembers 30, 40 with the two longitudinal rail parts 10, 20.

[0081] Deforming the combined form to form a unit roof ring 203 may comprise hot forming or hot stamping the combined form 5. Different microstructures can be created in a hot-formed roof ring. These different microstructures can be created by heating a combined form 5 above the austenitizing temperature. In some examples, quenching may be carried out during and after forming. Quenching may include cooling above a critical cooling rate so that a martensitic microstructure is obtained.

[0082] In some examples, different microstructures can be obtained by heating a combined format 5 above the austenitizing temperature and then controlling the cooling of the combined format 5 during forming the combined format 5 to form a unit roof ring 100. In some examples, quenching can be avoided on selected parts of the unit roof ring 100.

[0083] In some examples, deforming the combined format to form a unitary roof ring 203 can be accomplished in a single operation. The unitary roof ring 100 formed by deforming the combined format 203 includes two longitudinal rail parts, each connected to a front crossmember and a rear crossmember to form a substantially closed ring configuration.

[0084] For the sake of completeness, various aspects of this disclosure are set out in the following numbered clauses: Clause 1. A method for manufacturing a unitary roof ring 100 of a vehicle frame, the method comprising: provide a plurality of formats (1, 2, 3, 4); combine the formats to form a combined format (5); deform the combined format (5) to form the unitary roof ring (100); wherein the unitary roof ring (100) includes two longitudinal rail parts (10, 20) each connected to a front crossmember (30) and a rear crossmember (40) to form a substantially closed ring configuration. Clause 2. The procedure for manufacturing a unitary roof ring (100) according to clause 1, wherein joining the formats comprises forming one or more overlapping regions (6) formed by partially overlapping the formats with each other. Clause 3. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 2, wherein one of the overlapping regions (6) is formed at a joining point of the front crossmember (30) with one of the longitudinal rail parts (10, 20). Clause 4. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 3, wherein the overlap region (6) is formed substantially within the front crossmember (30). Clause 5. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 4, wherein the overlapping region (6) has a length L1 corresponding to a width of the longitudinal rail portion (10, 20) and has a width W1 of at least 5 cm. Clause 6. The procedure of any of clauses 3-5, wherein overlapping regions (6) are formed at each of the joining points of the front and rear crossmembers (30, 40) with the two longitudinal rail parts (10, 20). Clause 7. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-6, wherein joining the formats comprises welding the formats together. Clause 8. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 7, wherein the welding comprises resistance spot welding and / or laser welding. Clause 9. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-8, wherein deforming the combined format (5) to form the unitary roof ring (100) comprises hot stamping the combined format (5). Clause 10. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-9, wherein the deformation is carried out in a single operation. Clause 11. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-10, wherein the two longitudinal rail parts (10, 20) comprise the outer roof rail parts and wherein the front and rear crossmembers (30, 40) comprise the front and rear headrests of a vehicle frame. Clause 12. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-11, wherein the plurality of formats (1, 2, 3, 4) comprises two longitudinal beam formats (1, 2) and two transverse beam formats (3, 4). Clause 13. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 12, wherein the plurality of formats (1, 2, 3, 4) further comprises a central beam format (8). Clause 14. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-13, wherein a patch format (7) is joined to at least one of the plurality of formats (1, 2, 3, 4) to form the combined format (5). Clause 15. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 14, wherein the patch format (7) is arranged within the front and / or rear crossbeam format (3, 4). Clause 16. The procedure for manufacturing a unitary roof ring (100) in accordance with clause 15, wherein the patch format (7) is substantially disposed in a central part of the front and / or rear crossbeam formats (3, 4). Clause 17. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-16, wherein a thickness of the cross members (30, 40) is less than a thickness of the longitudinal rail parts (10, 20). Clause 18. The procedure for manufacturing a unitary roof ring (100) in accordance with any of clauses 1-17, wherein the thickness of the longitudinal rail parts (10, 20) and / or the thickness of the crossbars (30, 40) is 0.5-2.5 mm, specifically 1-1.8 mm. Clause 19. The process for manufacturing a unitary roof ring (100) according to any of clauses 1-18, wherein the plurality of formats (1, 2, 3, 4) is made of ultra-high-strength steel. Clause 20. The process for manufacturing a unitary roof ring (100) according to any of clauses 1-19, wherein the unitary roof ring (100) has a tensile strength of 150-2000 MPa. Clause 21. A unit roof ring (100) obtainable by a procedure in accordance with any of clauses 1 - 20. Clause 22. A roof ring (100) for a vehicle structural frame, having substantially a ring shape and comprising: a front crossbar (30), a rear crossmember (40), a first part of longitudinal rail (10) and a second part of longitudinal rail (20), in which the roof ring (100) is made by deforming a single format. Clause 23. A unitary roof ring (100) according to clause 21, wherein the unitary roof ring (100) is part of the upper frame of a vehicle. Clause 24. A vehicle comprising the unitary roof ring (100) in accordance with clause 21 or 22.

[0085] Although only a number of examples have been disclosed herein, other alternatives, modifications, uses, and / or equivalents are possible. Furthermore, all possible combinations of the described examples are also covered. Therefore, the scope of this disclosure should not be limited by particular examples but should be determined solely by an unbiased reading of the claims that follow.

Claims

1. A method for manufacturing a unitary roof ring (100) for a vehicle frame, the method comprising: providing a plurality of formats (1, 2, 3, 4); joining the formats to form a combined format (5); deforming the combined format (5) to form the unitary roof ring (100); wherein the unitary roof ring (100) includes two longitudinal rail portions (10, 20), each connected to a front crossmember (30) and a rear crossmember (40) to form a substantially closed ring configuration.

2. The method for manufacturing a unitary roof ring (100) according to claim 1, wherein joining the formats comprises forming one or more overlapping regions (6) by partially overlapping the formats with each other. 3.The method for manufacturing a unitary roof ring (100) according to claim 2, wherein one of the overlapping regions (6) is formed at a point where the front crossmember (30) joins one of the longitudinal rail portions (10, 20).

4. The method for manufacturing a unitary roof ring (100) according to claim 3, wherein the overlapping region (6) is formed substantially within the front crossmember (30).

5. The method for manufacturing a unitary roof ring (100) according to claim 4, wherein the overlapping region (6) has a length L1 corresponding to a width of the longitudinal rail portion (10, 20) and has a width W1 of at least 5 cm. 6.The method of any of claims 3-5, wherein overlapping regions (6) are formed at each of the joining points of the front and rear crossmembers (30, 40) with the two longitudinal rail portions (10, 20).

7. The method for manufacturing a unitary roof ring (100) according to any of claims 1-6, wherein joining the forms comprises welding the forms together, and optionally comprises resistance spot welding and / or laser welding.

8. The method for manufacturing a unitary roof ring (100) according to any of claims 1-7, wherein deforming the combined form (5) to form the unitary roof ring (100) comprises hot stamping the combined form (5). 9.The method for manufacturing a unitary roof ring (100) according to any of claims 1-8, wherein the plurality of formats (1, 2, 3, 4) comprises two longitudinal beam formats (1, 2) and two transverse beam formats (3, 4).

10. The method for manufacturing a unitary roof ring (100) according to any of claims 1-9, wherein a patch format (7) is joined to at least one of the plurality of formats (1, 2, 3, 4) to form the combined format (5), and optionally wherein the patch format (7) is disposed within the front and / or rear transverse beam format (3, 4).

11. The method for manufacturing a unitary roof ring (100) according to claim 10, wherein the patch format (7) is substantially disposed in a central portion of the front and / or rear crossbeam formats (3, 4). 12.The method for manufacturing a unitary roof ring (100) according to any of claims 1-11, wherein the thickness of the cross members (30, 40) is less than the thickness of the longitudinal rail portions (10, 20).

13. The method for manufacturing a unitary roof ring (100) according to any of claims 1-12, wherein the unitary roof ring (100) has a tensile strength of 150-2000 MPa.

14. A unitary roof ring (100) obtainable by a process according to any of claims 1-13.

15. A roof ring (100) for a structural frame of a vehicle, having substantially a ring shape and comprising: a front crossmember (30), a rear crossmember (40), a first longitudinal rail part (10) and a second longitudinal rail part (20), wherein the roof ring (100) is made by deforming a single shape.

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