Vehicle dash panel assembly

Abstract

A dash panel assembly (1) for a motor vehicle (100), the dash panel assembly (1) comprising a lower dash panel (21) and an upper dash panel (22), each of the lower and upper dash panels (21, 22) being fabricated by forming a single metal plate, the lower dash panel (21) further comprising a lower portion (211) and an overlapping portion (212), and the upper dash panel (22) further comprising an upper portion (221) and an overlapping portion (222). A dash panel assembly (1) for an automotive vehicle (100) in which, when assembled to form the dash panel assembly (1), the lower and upper dash panels (21, 22) overlap each other at their respective overlapping portions (212, 222) to form an overlapping portion (12) of the dash panel assembly, and do not overlap each other at the lower portion of the lower dash panel (211) and the upper portion of the upper dash panel (221).

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to structural components for motor vehicles, and more particularly to vehicle dash panel assemblies. [Background technology]

[0002] Automakers are facing increasingly stringent requirements. They are being asked to increase the passive safety of their vehicles while simultaneously lowering vehicle weight, either to minimize greenhouse gas emissions in the case of internal combustion engines or to extend the vehicle's driving range in the case of electric vehicles. At the same time, vehicle production costs must remain low and production speeds must be fast. Furthermore, automakers are looking to simplify vehicle production by reducing the number of individual parts that make up a vehicle.

[0003] The dash panel assembly separates the front motor compartment from the passenger compartment. It is a large assembly with several subcomponents, typically around ten individual subcomponents. It extends across the entire width of the vehicle and a substantial portion of the vehicle's elevation. It is responsible for absorbing crash energy and resisting intrusion in the event of a frontal or side impact. It is a critical structural element and one of the key components in ensuring passenger safety. It also plays a key role in ensuring the overall rigidity of the body-in-white.

[0004] Dash panel assemblies contribute to improving the safety performance of a vehicle in various regulatory tests, such as:

[0005] 64. The Insurance Institute for Highway Safety (IIHS) Small Overlap Rigid Barrier (SORB) crash involves an impact with a rigid barrier moving at 4 km / h, overlapping only 25% of the vehicle's width.

[0006] 64. IIHS Front Overlapping Deformable Barrier (ODB) impact with a rigid barrier moving at 4 km / h, overlapping just 40% of the vehicle's width.

[0007] The US New Car Assessment Program (USNCAP) pole test involves a vehicle with an initial lateral speed of 32.2 km / h colliding sideways with a fixed pole and impacting it.

[0008] IIHS's Mobile Deformable Barrier (MDB) test, in which the side of a vehicle is impacted by a deformable barrier weighing 1500 kg and traveling at a speed of 50 km / h.

[0009] These tests themselves are becoming increasingly stringent with ever higher impact energies and more stringent requirements. Summary of the Invention [Problem to be solved by the invention]

[0010] SUMMARY OF THE INVENTION It is an object of the present invention to provide a dash panel assembly having very high crashworthiness. It is also an object of the present invention to provide a vehicle having a dash panel assembly according to the present invention.

[0011] It is also an object of the present invention to provide a dash panel assembly that is lighter than current designs, thereby saving fuel in the case of combustion engines and increasing mileage in the case of electric engine powered vehicles.

[0012] Furthermore, it is an object of the present invention to address the challenges of increased productivity, reduced complexity, and reduced costs in vehicle production. Indeed, the present invention provides a dash panel assembly with fewer parts than the baseline design. The design of the present invention can be produced and assembled in significantly fewer manufacturing steps compared to the baseline. In addition to simplifying production, reducing costs, and increasing productivity, reducing the number of production steps reduces the environmental impact of the production process and reduces the overall CO2 emissions when manufacturing a vehicle.

[0013] The object of the present invention is achieved by providing a dash panel assembly as set forth in claim 1, optionally including the features of claims 2 to 4 taken individually or according to any possible combination. A further object of the present invention is achieved by providing a motor vehicle as set forth in claim 5. [Means for solving the problem]

[0014] In the following description and claims, directional terms are defined according to the normal directions of the vehicle in which they are installed.

[0015] In particular, terms such as "top," "upper," "upper," "bottom," "lower," "below" and "belower" are defined according to the elevation direction of the vehicle. Terms such as "front," "rear," "rearward," "front," "forward," "rearward" and the like are defined according to the longitudinal direction of the vehicle, i.e., the direction in which the vehicle moves when following a straight line. Terms such as "left side," "right side," and "lateral" are defined according to an orientation parallel to the width of the vehicle. The terms "inner" and "outer" should be understood according to the width direction of the vehicle, with "inner" being closest to the vehicle's central axis, i.e., closest to the interior of the vehicle, while "outer" is located further away from said central axis of the vehicle, effectively closer to the outside of the vehicle. The same applies to the terms "distal" and "central," with a "distal" part being closest to the outside of the vehicle and a "central" part being closest to the center of the vehicle. The term "horizontal" refers to an orientation in a plane including the longitudinal and lateral directions. The term "vertical" refers to any orientation including the elevation direction.

[0016] In the following figures, all orientation and spatial references are made using an X, Y, Z coordinate reference system, where Z is the vehicle's elevation direction, X is the vehicle's longitudinal direction, and Y is the vehicle's lateral direction. The reference system is represented on each figure. If the figure is a 2D flat representation, the outer axis of the figure is, according to established convention, represented by a dot in a circle when it is pointing towards the reader, and by a cross in a circle when it is pointing away from the reader.

[0017] By "substantially parallel" or "substantially perpendicular" is meant a direction that can deviate from the parallel or perpendicular direction by no more than 15°.

[0018] A steel plate refers to a flat steel plate. The steel plate has a top surface and a bottom surface, also called the top and bottom sides or the top and bottom surfaces. The distance between the surfaces is designated as the thickness of the plate. The thickness can be measured, for example, using a micrometer, the spindle and anvil of which are positioned on the top and bottom surfaces. Similarly, the thickness can also be measured on the formed part.

[0019] By average thickness of a part or portion of a part, we mean the overall average thickness of the material that makes up the part after it has been initially formed from a flat sheet into a three-dimensional part.

[0020] Tailor welded blanks are made by assembling several plates or cut blanks of steel, known as sub-blanks, together, for example by laser welding, to optimize part performance in different areas, reduce the overall part weight, and lower the overall part cost. The sub-blanks that form the tailored welded blank can be assembled with or without overlap, for example, they can be laser butt welded (no overlap) or spot welded to each other (with overlap).

[0021] In contrast to a tailored welded blank, a monolithic blank refers to a blank that consists of one single sub-blank, rather than multiple sub-blanks joined together.

[0022] Tailor rolled blanks are blanks with multiple thicknesses obtained by differential rolling during the steel plate production process.

[0023] Ultimate tensile strength, yield strength, and elongation are measured according to ISO standard ISO 6892-1, published in October 2009. Tensile specimens are cut from the flat area. If necessary, smaller tensile test samples are taken to fit the entire available flat area of ​​the part.

[0024] The bending angle is measured according to the VDA-238 bending standard. For the same material, the bending angle depends on the thickness. For simplicity, the bending angle value in this invention refers to a thickness of 1.5 mm. If the thickness is different from 1.5 mm, the bending angle value should be normalized to 1.5 mm by the following calculation: α1.5 is the bending angle normalized to 1.5 mm, t is the thickness, and αt is the bending angle for thickness t.

[0025] α1.5=(αt×√t) / √1.5

[0026] Hot stamping is a steel forming technique that involves heating a steel blank, or a pre-formed part made from a steel blank, to a temperature at which the microstructure of the steel is at least partially converted to austenite, forming the blank or pre-formed part at high temperature by stamping and simultaneously quenching the formed part to obtain a microstructure with very high strength, possibly with an additional division or tempering step in the heat treatment.

[0027] A multi-step hot stamping process is a specific type of hot stamping process consisting of at least two process steps, including at least one stamping step, performed at temperatures above 300°C. For example, a multi-step process can involve a first stamping operation and a subsequent hot trimming operation, so that at the end of the hot stamping process, the finished part does not require further trimming. For example, a multi-step process can involve several consecutive stamping steps to produce parts with more complex shapes than can be achieved using a single stamping operation. For example, parts are automatically transferred from one operation to another in a multi-step process, using, for example, a transfer press. For example, the part remains in the same tool, which is a multi-purpose tool that can perform various operations, such as the initial stamping and subsequent in-tool trimming operations. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view of a motor vehicle highlighting the location of a dash panel assembly. [Figure 2] FIG. 2 is a perspective view of the dash panel assembly and its surrounding components. [Figure 3]1 is a perspective view of a dash panel assembly according to the state of the art, in this case fully assembled. [Figure 4] FIG. 1 is a perspective view of a dash panel assembly according to the state of the art, where the different individual components joined together from the dash panel assembly are offset from each other to clearly and separately represent each. [Figure 5] 1 is a perspective view of one embodiment of a dash panel assembly according to the present invention, where the dash panel assembly is fully assembled. [Figure 6] FIG. 1 is a perspective view of one embodiment of a dash panel assembly according to the present invention, where different individual components joined together from the dash panel assembly are offset from one another to clearly and separately represent each. [Figure 7A] 6 is a right-side perspective view of a dash panel assembly according to the present invention after cutting the left side of the dash panel according to the plane AA defined in FIG. 5. FIG. [Figure 7B] 6 is a schematic cross-sectional view of a dash panel assembly according to the present invention taken along the cross section AA defined in FIG. 5. [Figure 8A] 1 is a schematic diagram of one embodiment of a tailored welded blank used to manufacture an upper dash panel in accordance with the present invention. FIG. [Figure 8B] 1 is a schematic diagram of one embodiment of a tailored welded blank used to manufacture a lower dash panel in accordance with the present invention. FIG. [Figure 9A] FIG. 1 is a perspective view of a simulated IIHS front overlap deformable barrier (ODB) crash test at time t=0 s, i.e., just before the barrier impacts the vehicle. [Figure 9B] Although the same is represented, only the front motor and dash panel assembly is shown to focus on the interaction between these two elements during crash testing. [Figure 10A] The progression of the aforementioned crash test simulation is shown at t=0.085 s and t=0.105 s. [Figure 10B] The progression of the aforementioned crash test simulation is shown at t=0.085 s and t=0.105 s. [Figure 11A] The progression of the aforementioned crash test simulation is shown at t=0.085 s and t=0.105 s. [Figure 11B] The progression of the aforementioned crash test simulation is shown at t=0.085 s and t=0.105 s. DETAILED DESCRIPTION OF THE INVENTION

[0029] 1 and 2, the passenger compartment 101 of a motor vehicle 100 is a volume accessible to vehicle occupants. The front motor compartment 102 of the vehicle 100 is a volume located at the front of the vehicle, extending laterally across the width of the vehicle and longitudinally from the front bumper (not shown) to the passenger compartment 101. This is commonly referred to as the front motor compartment or front engine compartment, but in fact may not include an engine or motor in some vehicles (e.g., in the case of vehicles with an engine or motor mounted in the rear, in the center, or directly on the wheels). In this case, it may function as a storage compartment, sometimes referred to as the "frunk." It is typically closed off by a hood (not shown) on top.

[0030] For obvious safety reasons, the passenger compartment 101 needs to be protected in the event of a collision. The lower part of the passenger compartment is bounded by a floor panel 3 that extends laterally between the left and right side sills 6. In the case of electric vehicles, a high voltage (HV) battery housing is typically located below the floor panel 3.

[0031] The dash panel assembly 1 is a structural component that delimits the passenger compartment 101 at its lower front end and separates the passenger compartment 101 from the front motor compartment 102. The dash panel assembly 1 is also known as a firewall or cowl. It extends substantially longitudinally and in elevation between the floor panel 3 and the windshield (not shown). As shown in FIG. 2, an intermediate component, such as a cowl upper 4, may be provided between the dash panel assembly 1 and the windshield. The cowl upper may be dedicated to supporting, for example, the windshield and / or hood hinges. In any case, the cowl upper does not serve as a primary structural component in the vehicle, particularly in the case of a frontal impact in which elements located inside the front motor compartment are pushed rearward and impact the dash panel.

[0032] The dash panel assembly 1 occupies the entire lateral space of the vehicle. As shown in Figure 2, it is located between the left and right side sills 6 and the left and right lower A-pillars 2. It is generally attached to the following elements of the body-in-white:

[0033] Left and right front members 5 and left and right upper fender rails 7 at the front; Left and right side sills 6 and left and right lower A-pillars 2 at the sides; Towards the rear of the vehicle, a floor panel 3, a tunnel nose 8 (which may not be present in the case of a fully electric vehicle) and a floor reinforcement member attached to the floor panel 3, not shown in the accompanying drawings.

[0034] It should be noted that the above list of connecting components is not limiting and is not necessarily comprehensive, as it depends on the selected design of the vehicle architecture. The present invention specifically addresses dash panel assembly 1 and can be applied to dash panel assemblies connected to various types of surrounding components. In either case, what is important is that dash panel assembly 1 occupies a central position within the vehicle's front load path, absorbing significant forces from frontal crash structures, such as front member 5 and upper fender rail 7. It also occupies a central position within the front lateral load path, for example, between the front of side sill 6 and the front majority of lower A-pillar 2. Thus, the dash panel assembly is a fundamental component of the vehicle's front and side crash systems, responsible for absorbing, transferring, and dissipating crash energy. It is also a critical intrusion prevention component, since it is located between the front motor track and the vehicle's front occupants in the event of a frontal impact. If the motor were not located within the front motor compartment 102, it would be directly between the passenger compartment and the element impacting the vehicle.

[0035] Referring to Figure 3, a state-of-the-art dash panel assembly 1, the dash panel assembly typically has a substantially curved shape, with the upper portion located further forward of the vehicle than the lower portion. It also usually has several openings communicating with the front motor compartment, such as opening 9 through which the pedal mechanism is inserted, or opening 10 through which the steering column is inserted.

[0036] Referring to Figure 4, which is an exploded view of a state-of-the-art dash panel assembly, the state-of-the-art dash panel assembly is made up of many individual parts that are assembled together, for example, by spot welding. In the example of Figures 3 and 4, ten individual parts make up the dash panel assembly.

[0037] Left and right lower parts 11, Lower center 12, Left and right side brackets 13, Reinforcement cross beam 14, Left and right upper parts 15, Upper center part 16, Upper right reinforcement section 17.

[0038] In the event of a frontal impact, the front motor is pushed rearward toward the passenger compartment, and the reinforcing cross beam 14 plays a key role in resisting intrusion. The reinforcing cross beam 14 generally has an omega shape, and when combined with the remaining subcomponents, it forms a laterally extending hollow body that efficiently resists intrusion. The left and right side brackets 13 also form hollow bodies on the sides of the dash panel assembly, which provide additional resistance to intrusion in the event of a small widthwise overlap impact, which essentially concentrates energy on only one side of the dash panel assembly. Furthermore, the side brackets 13 form a robust assembly with the lower A-pillar, helping to improve the vehicle's crashworthiness in side impacts.

[0039] The upper right reinforcement 17 serves to provide additional rigidity to the area that supports the pedal mechanism.

[0040] The aforementioned dash panel assembly design comprises a large number of individual sub-components, which leads to a complex logistics and manufacturing chain. This also represents a high cost in terms of tooling costs to form the individual components and in terms of assembly to join them all together. Furthermore, because the components are joined together by, for example, spot welds, they may tear apart in the event of significant stresses that arise during the vehicle's life, such as stresses caused by impact or simple repeated fatigue stresses. Therefore, the presence of a large number of sub-components is also a source of potential structural weakness.

[0041] 5 and 6, the dash panel assembly according to the present invention, in comparison, includes only two components: a lower dash panel 21 and an upper dash panel 22. The lower dash panel 21 and the upper dash panel 22 are each fabricated by forming a single metal plate. For example, at least one of them is manufactured by hot stamping a single metal plate. For example, at least one of them is manufactured by hot stamping a single metal plate using a multi-step process. For example, at least one of them is manufactured by stamping a tailored welded blank. For example, at least one of them is manufactured by stamping a tailored rolled blank.

[0042] 6, lower dash panel 21 includes lower portion 211 and overlapping portion 212 located at the top of lower dash panel 21. Upper dash panel 22 includes upper portion 221 and overlapping portion 222 located at the bottom of upper dash panel 22. When assembled, lower and upper dash panel overlapping portions 212 and 222 overlap one another (hence the term overlap). The portion of dash panel assembly 1 where the lower and upper dash panels overlap is referred to as overlapping portion 12. However, when the dash panels are assembled, the lower portion of lower dash panel 211 and the upper portion of upper dash panel 221 do not overlap one another.

[0043] 7B, a schematic cross-sectional view of dash panel assembly 1 according to the present invention, overlap portion 12 includes at least one flat overlap area 122 in which upper and lower dash panels 21 and 22 lie flat on top of each other. In other words, in at least one flat overlap area 122 of overlap portion 12, dash panel lower overlap portion 212 and dash panel upper overlap portion 222 have the same shape, so that when assembled, they fit flat against each other within said flat overlap area 122. The upper and lower dash panels 22, 21 can be assembled together within at least one flat overlap area 122 by, for example, resistance spot welding or laser welding. The flat overlap area 122 further presents the technical advantage of significantly increasing intrusion resistance, since two layers of formed sheet metal are available to jointly resist intrusion within this area.

[0044] 7A and 7B, overlap area 12 further includes at least one hollow portion 120, in which overlapping portions of upper and lower dash panels 212 and 222 are longitudinally spaced apart from one another to together define an interior volume contained therebetween. Advantageously, the presence of hollow portion 120 increases the overall rigidity of dash panel assembly 1 and allows it to better resist intrusion. Indeed, the presence of hollow portion 120 confers rigidity to the dash panel assembly, making deformation at said hollow portion more difficult.

[0045] In the accompanying drawings, hollow portion 120 is formed by designing dash panel upper overlap portion 212 with substantially horizontal walls across the entire width of the part, and by designing substantially horizontal walls in the side sections of dash panel lower overlap portion 222, the central portion of which remains substantially flat in hollow portion 120 and acts as a flat closing plate for the interior volume. Advantageously, this design allows for a larger hollow volume within the sides of the dash panel assembly, providing better side intrusion resistance. This is particularly useful in frontal impacts where the overlap is small and loads are primarily applied to only one side of the part.

[0046] For example, the hollow portion 120 can be designed differently by using a rounded bead-like shape in the corresponding dash panel lower and / or upper overlapping portions 222, 212.

[0047] Generally speaking, the amount of collision energy absorption and the resistance to intrusion are greater when the horizontal walls are designed with sheet metal having the greatest mechanical resistance, for example, when the horizontal walls are designed with sheet metal having the greatest thickness, or the greatest yield strength, or the greatest product of yield strength and sheet metal thickness.

[0048] The design of the present invention allows for a significant simplification of the conception and manufacturing process of the dash panel assembly by reducing the number of sub-components, which in turn allows for a significant reduction in the number of assembly points between the sub-components.

[0049] The reduction in the number of overlapping areas required to assemble the different sub-components, combined with the optimal choice of materials, leads to a significant weight reduction in the assembly.

[0050] Furthermore, the inventive design simplifies and reproduces important safety features of state-of-the-art designs, particularly the reinforcement in the central portion of the dash panel assembly. Said reinforcement is ensured, for example, by the reinforcing cross beam 14 of the state-of-the-art design. In the inventive design, said reinforcement is ensured by doubling the plate thickness in the overlapping portion 12, optionally reinforced by the presence of a hollow portion 120 in the overlapping portion 12. The overlapping portion 12 of the inventive design makes it possible to prevent the front motor from penetrating the passenger compartment 101. It also increases the overall stiffness of the part, making it possible to withstand lateral compressive loads exerted on the part in the event of a side impact.

[0051] In a specific embodiment, the dash panel assembly is manufactured by hot stamping steel sheet, and the blanks used to produce it include one of the following materials, either in the form of a monolithic blank or combined in the form of a tailored welded blank:

[0052] This steel has a composition of 0.06% by weight or less C ≤ 0.1% by weight, 1% by weight or less Mn ≤ 2% by weight, ≤ 0.5% by weight Si ≤ 0.1% by weight, 0.02% by weight or less Cr ≤ 0.1% by weight, 0.02% by weight or less Nb ≤ 0.1% by weight, 0.0003% by weight or less B ≤ 0.01% by weight, ≤ 0.01% by weight N ≤ 0.003% by weight S ≤ 0.020% by weight P, and contains less than 0.1% by weight Cu, Ni, and Mo, with the remainder being iron and unavoidable impurities resulting from refining. Within this composition range, the yield strength of the corresponding area after hot stamping is between 700 and 950 MPa, the tensile strength is between 950 and 1200 MPa, and the bend angle is greater than 75°. For example, this material is used in the area corresponding to the upper portion 221 of the upper dash panel because it will absorb energy without cracking and this area does not need to withstand as much penetration as the upper dash panel overlap portion 222.

[0053] A steel having an ultimate tensile strength after hot stamping of 1300 MPa to 1650 MPa and a yield strength of 950 MPa to 1250 MPa.

[0054] A steel having an ultimate tensile strength after hot stamping comprised between 1300 MPa and 1650 MPa, a yield strength comprised between 950 MPa and 1250 MPa, and a bending angle of more than 75°.

[0055] A steel having a composition including 0.20 wt%≦C≦0.25 wt%, 1.1 wt%≦Mn≦1.4 wt%, 0.15 wt%≦Si≦0.35 wt%, Cr≦0.30 wt%, 0.020 wt%≦Ti≦0.060 wt%, 0.020 wt%≦Al≦0.060 wt%, S≦0.005 wt%, P≦0.025 wt%, and 0.002 wt%≦B≦0.004 wt%, with the remainder being iron and unavoidable impurities resulting from refining. In this composition range, the ultimate tensile strength of the corresponding area of ​​the part after hot stamping is between 1300 MPa and 1650 MPa, and the yield strength is between 950 MPa and 1250 MPa. For example, this steel composition is used for the area corresponding to the overlap portion 12 of the dash panel assembly (i.e., for the steel constituting the overlap portions 212 and 222 of the lower and upper dash panel). In fact, this steel grade has high anti-penetration properties.

[0056] Steel with a tensile strength of more than 1800 MPa after press hardening.

[0057] The steel has a composition including 0.24 wt% < C < 0.38 wt%, 0.40 wt% < Mn < 3 wt%, 0.10 wt% < Si < 0.70 wt%, 0.015 wt% < Al < 0.070 wt%, Cr < 2 wt%, 0.25 wt% < Ni < 2 wt%, 0.015 wt% < Ti < 0.10 wt%, Nb < 0.060 wt%, 0.0005 wt% < B < 0.0040 wt%, 0.003 wt% < N < 0.010 wt%, S < 0.005 wt%, and P < 0.025 wt%, with the remainder being iron and unavoidable impurities resulting from refining. In this composition range, the tensile strength of the corresponding area of ​​the dash panel assembly after hot stamping is greater than 1800 MPa. For example, this material is used for the overlap portion 12 to benefit from its high anti-intrusion properties.

[0058] A steel having a composition including 0.15-0.25 wt% C, 0.5-1.8 wt% Mn, 0.1-1.25 wt% Si, 0.01-0.1 wt% Al, 0.1-1.0 wt% Cr, 0.01-0.1 wt% Ti, 0.001-0.004 wt% B, P≦0.020 wt%, S≦0.010 wt%, N≦0.010 wt%, and optionally one or more of the following elements: Mo≦0.40 wt%, Nb≦0.08 wt%, Ca≦0.1 wt%, with the remainder being iron and unavoidable impurities resulting from refining. With this composition range, the tensile strength of the corresponding area of ​​the dash panel assembly after hot stamping is greater than 1350 MPa, and the bend angle is greater than 70°.

[0059] A steel having a composition including 0.26-0.40 wt% C, 0.5-1.8 wt% Mn, 0.1-1.25 wt% Si, 0.01-0.1 wt% Al, 0.1-1.0 wt% Cr, 0.01-0.1 wt% Ti, 0.001-0.004 wt% B, P≦0.020 wt%, S≦0.010 wt%, N≦0.010 wt%, and optionally one or more of the following elements: Ni≦0.5 wt%, Mo≦0.40 wt%, Nb≦0.08 wt%, Ca≦0.1 wt%, with the remainder being iron and unavoidable impurities resulting from refining. With this composition range, the tensile strength of the corresponding area of ​​the dash panel assembly after hot stamping is greater than 1350 MPa, and the bend angle is greater than 70°.

[0060] A steel having a composition including 0.2-0.34 wt% C, 0.50-1.24 wt% Mn, 0.5-2 wt% Si, P≦0.020 wt%, S≦0.010 wt%, and N≦0.010 wt%, and optionally including one or more of the following elements: Al≦0.2 wt%, Cr≦0.8 wt%, Nb≦0.06 wt%, Ti≦0.06 wt%, B≦0.005 wt%, and Mo≦0.35 wt%, with the remainder being iron and unavoidable impurities resulting from refining. With this composition range, the tensile strength of the corresponding area of ​​the dash panel assembly after hot stamping is 1000 MPa or more, and the bend angle is greater than 55°.

[0061] A steel having a composition including 0.13-0.4 weight% C, 0.4-4.2 weight% Mn, 0.1-2.5 weight% Si, Cr≦2 weight%, Mo≦0.65 weight%, Nb≦0.1 weight%, Al≦3.0 weight%, Ti≦0.1 weight%, B≦0.005 weight%, P≦0.025 weight%, S≦0.01 weight%, N≦0.01 weight%, Ni≦2.0 weight%, Ca≦0.1 weight%, W≦0.30 weight%, V≦0.1 weight%, and Cu≦0.2 weight%, the following combination was verified: 114-68*C-18*Mn+20*Si-56*Cr-60*Ni-36*Al+38*Mo+79*Nb-17691*B<20, with the remainder of the composition being iron and unavoidable impurities resulting from refining. For example, the composition is used when hot stamping parts using a multi-step process.

[0062] Steel coated with an aluminum-based metallic coating. Aluminum-based means a coating containing at least 50% aluminum by weight. For example, the metallic coating is an aluminum-based coating containing 8-12% silicon by weight. The metallic coating is applied, for example, by immersing the substrate in a molten metal bath. Advantageously, applying an aluminum-based metallic coating avoids the formation of surface scale during the heating step of the hot stamping process, which in turn allows parts to be produced by hot stamping without a subsequent sandblasting operation. Furthermore, the aluminum-based coating also provides corrosion protection for the part while the vehicle is in service.

[0063] 1. A steel coated with an aluminum-based metallic coating containing 2.0 to 24.0 weight percent zinc, 1.1 to 12.0 weight percent silicon, optionally 0 to 8.0 weight percent magnesium, and optionally an additional element selected from Pb, Ni, Zr, or Hf, the weight content of each additional element being less than 0.3 weight percent, the remainder being aluminum and optionally unavoidable impurities. Advantageously, this type of metallic coating provides the part with very good corrosion protection and a good surface aspect after hot stamping.

[0064] In a specific embodiment, at least the upper or lower dash panel is manufactured by hot stamping a laser-welded blank comprising at least one sub-blank with an aluminum-based metallic coating, said aluminum-coated sub-blank having been previously prepared by ablating at least part of the metallic coating on the edges to be welded, advantageously removing part of the aluminum present in the coating that could contaminate the weld seam and deteriorate its mechanical properties.

[0065] In a specific embodiment, at least one of the upper and lower dash panels is manufactured by hot stamping a laser-welded blank comprising at least one sub-blank, at least one side of which is covered with an emissivity-increasing top layer. The emissivity-increasing top layer is applied to the outermost surface of the sub-blank. The emissivity-increasing top layer allows the surface of the sub-blank to have a higher emissivity compared to the same sub-blank not coated with the emissivity-increasing top layer. The emissivity-increasing top layer can be applied to either the top side or the bottom side of the sub-blank. The emissivity-increasing top layer can also be applied to both sides of the sub-blank. If the sub-blank comprises a metal coating as described above, the emissivity-increasing top layer is applied on top of the metal coating. In fact, the emissivity-increasing top layer needs to cover the outermost surface of the sub-blank to increase the emissivity of the surface. Advantageously, the emissivity-increasing top layer allows for an increased heating rate of the sub-blank, thus improving the productivity of the heating step of the hot stamping process. When using several sub-blanks of different thicknesses, said emissivity-increasing top layer is advantageously applied to the thickest sub-blank in order to reduce the difference in heating time between the different sub-blanks and thus increase productivity, widen the process window of hot stamping and make it possible to obtain a final part with overall uniform surface properties.

[0066] In a particular embodiment, the upper and lower dash panels are manufactured by hot stamping tailored welded blanks, as shown schematically in Figures 8A and 8B, respectively. Steel grades and thicknesses are described in further detail by reference to the following table (which can be produced using the above detailed embodiment of the steel grade chemistries):

[0067] [Table 1]

[0068] Steel D1000 has a lower yield strength but a higher bending angle, and therefore deforms and absorbs energy more easily than steel U1500. On the other hand, steel U1500 has a better anti-penetration effect than D1000 due to its higher strength.

[0069] Referring to FIG. 8A, the tailored welded blank used for upper dash panel 22 consists of three sub-blanks 221A, 221B, and 222A having the following grades and thicknesses:

[0070] [Table 2]

[0071] Sub-blanks 221A and 221B correspond to the upper portion 221 of the upper dash panel top when the part is formed, while sub-blank 222A corresponds to the overlap portion 222 of the upper dash panel top when the part is formed.

[0072] As previously explained, the anti-intrusion function of the dash panel assembly is primarily ensured by the overlapping portion 12. Accordingly, the sub-blank 222A in this embodiment is made of very high-strength steel grade D1500 and has a large thickness of 2.5 mm. Furthermore, in this embodiment, once formed, the overlapping portion 222 of the upper dash panel has substantially horizontal walls to form the hollow portion 120 within the overlapping portion 12. As in this embodiment, selecting a very high-strength, large-thickness material for this section advantageously improves the rigidity and anti-intrusion function of the part.

[0073] On the other hand, the upper portion of the upper dash panel would be able to deform without cracking during a frontal impact to absorb energy. Therefore, steel grade D1000 was selected for sub-blanks 221A and 221B. Furthermore, because 221A is located in the area where the pedal mechanism is inserted, a greater thickness was selected for this sub-blank to increase the rigidity of this area.

[0074] Since sub-blank 222A has a significantly greater thickness than the other sub-blanks, it is interesting to provide the above-mentioned emissivity-increasing top layer on at least one side of sub-blank 222A to ensure that the heating rate in the austenitizing furnace of all areas of the tailored welded blank is as uniform as possible.

[0075] Turning to the lower dash panel 21, the tailored welded blank used to manufacture it consists of four sub-blanks 212A, 212B, 211A, 211B and 21A having the following grades and thicknesses:

[0076] [Table 3]

[0077] Sub-blanks 212A and 212B correspond to overlapping portion 212 of the upper part of the lower dash panel when the part is formed, while sub-blanks 211A and 211B correspond to lower portion 211 of the lower dash panel when the part is formed. Sub-blank 21A spans both the overlapping and lower portions when the part is formed.

[0078] As can be seen, the material thickness is greater for the sub-blanks (212A, 212B, 211A, 211B) that occupy the sides of the part than for the sub-blank (21A) that occupies the center of the part. This is to provide the part with better resistance in the event of a partial overlap crash, such as that simulated by the ODB or SORB regulatory tests detailed above. Furthermore, the blanks 212A, 212B corresponding to the sides of the overlap have a greater thickness than the blanks corresponding to the bottom portion, since they need to have higher penetration resistance at the overlap.

[0079] The above-described embodiment allows for a significant reduction in the number of spot welds for assembling the dash panel, for example, from 158 spot welds in the presented state-of-the-art assembly (see FIGS. 3 and 4) to 80 spot welds in this embodiment of the invention (FIGS. 5 and 6).

[0080] It also allows for an overall weight reduction, with the state-of-the-art assembly weighing 18.70 kg, while our design weighs 17.34 kg, a significant weight reduction of 7%.

[0081] The inventors have found that in the above-cited IIHS ODB and SORB crash tests, it is possible to achieve the same safety performance between the above-cited 18.70 kg state-of-the-art design and the 17.34 kg inventive design, demonstrating that the inventive design can achieve a better compromise between safety performance and component weight than the state-of-the-art.

[0082] 9A-9B through 11A-11B depict a simulated IIHS front overlap deformable barrier (ODB) crash test involving the above detailed and specific embodiment of the present invention, in which a vehicle was impacted with a rigid barrier moving at 64.4 km / h for only a 40% width overlap (barrier not shown in the figures for clarity).

[0083] At the start of the test, just before the barrier impacts the vehicle (Figures 9A and 9B), the motor 18 is positioned a distance away from the dash panel assembly 1. As the impactor impacts the vehicle, it pushes the motor 18 backward toward the vehicle compartment, eventually striking the dash panel assembly 1 at t = 0.085 s (Figures 10A and 10B). As can be seen, the impact also has the effect of tilting the motor 18 at an angle. At t = 0.105 s, the impactor reaches its maximum penetration depth (Figures 11A and 11B). The simulation shows that the dash panel assembly, particularly the overlapping portion 12, prevents the motor from penetrating the passenger compartment. The upper and lower dash panels dent due to the pressure exerted by the motor, but there is no significant penetration, and the overlapping portion 12 remains robust.

Claims

1. A dash panel assembly (1) for a motor vehicle (100), the dash panel assembly (1) occupies an entire lateral space of the motor vehicle between left and right side sills (6) and between left and right lower A-pillars (2), the dash panel assembly (1) separates a front motor compartment (102) from a passenger compartment (101), and comprises a lower dash panel (21) and an upper dash panel (22); the lower and upper dash panels (21, 22) are each made by forming a single metal plate; the lower dash panel (21) further comprises a lower portion (211) and an overlapping portion (212); the upper dash panel (22) further comprises an upper portion (221) and an overlapping portion (222); When assembled to form a dash panel assembly (1), the lower and upper dash panels (21, 22) overlap each other at their respective overlapping portions (212, 222) to form an overlapping portion (12) of the dash panel assembly, and do not overlap each other at the lower portion of the lower dash panel (211) and the upper portion of the upper dash panel (221); The overlapping portion (12) of the dash panel assembly (1) comprises at least one flat overlapping portion (122) where the lower and upper dash panels (11, 12) lie flat on top of each other. A dash panel assembly (1) for a motor vehicle (100).

2. 2. The dash panel assembly (1) for a motor vehicle (100) according to claim 1, wherein at least one of the lower and upper dash panels (21, 22) is fabricated by stamping a tailored welded blank.

3. A dash panel assembly (1) for a motor vehicle (100) according to claim 1 or 2, wherein at least one of the lower and upper dash panels (21, 22) is made by hot stamping.

4. 4. A dash panel assembly (1) for a motor vehicle (100) as recited in any one of claims 1 to 3, wherein the overlapping portion (12) further comprises a hollow portion (120) in which the lower and upper dash panel overlapping portions (212, 222) are longitudinally spaced from each other to form a hollow volume between the lower and upper dash panel overlapping portions.

5. A motor vehicle (100) comprising a dash panel assembly (1) according to any one of claims 1 to 4.

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