Vehicle's motor shield assembly

Abstract

FIELD: passenger vehicles.SUBSTANCE: relates to the vehicle's motor shield assembly. The motor shield separates the front engine compartment from the passenger compartment and consists of a lower motor shield and an upper motor shield. Each of the lower and upper parts of the motor shield is made by molding a separate metal sheet. The lower part of the motor shield contains a lower section and a cover section. The upper part of the motor shield contains an upper section and a cover section. After mounting the motor shield assembly, the lower and upper parts of the motor shield overlap each other at the corresponding overlapping sections to form the overlapping section of the motor shield assembly and do not overlap each other at the lower section of the lower part of the motor shield and the upper section of the upper part of the motor shield. The overlap section of the assembled motor shield comprises a flat overlap area in which the lower part and the upper part of the motor shield are plane-parallel adjacent to each other. The overlap section comprises a hollow section in which the overlap sections of the lower and upper parts of the assembled motor shield are located at a distance from each other in the longitudinal direction to form a hollow volume between them.EFFECT: increased collision safety.4 cl, 11 dwg

Description

[0001] The invention relates to structural parts of a mechanical vehicle and, in particular, to an assembled engine shield of a vehicle.

[0002] Automotive manufacturers are facing increasingly stringent demands. These include improving vehicle passive safety while simultaneously reducing vehicle weight to minimize greenhouse gas emissions for internal combustion engines and increasing range for electric vehicles. At the same time, vehicle production costs must be kept low and productivity high. Furthermore, automakers are striving to simplify vehicle manufacturing by reducing the number of individual component parts required for vehicle production.

[0003] The firewall assembly separates the front engine compartment from the passenger compartment. This large assembly contains several sub-assemblies, typically around ten individual sub-assemblies. It extends across the entire width of the vehicle and over a significant vertical section. It absorbs impact energy and prevents component penetration in the event of a frontal or side impact. It is a critical structural element and a key component in ensuring occupant safety. It also plays a significant role in ensuring the overall rigidity of the body after painting.

[0004] The engine shield assembly is related to improving the safety performance of the vehicle under various regulatory tests such as:

[0005] – Small Overlap Rigid Barrier Impact (SORB) tests developed by the Insurance Institute for Highway Safety (IIHS) in which a vehicle is impacted with only a 25% overlap in width against a rigid barrier traveling at 40 mph (64.4 km / h),

[0006] – IIHS Overlap Deformable Barrier (ODB) Frontal Impact Test, which involves a vehicle being impacted with only a 40% width overlap by a deformable barrier traveling at 40 mph (64.4 km / h),

[0007] – The US New Car Assessment Program (USNCAP) fixed pole impact test, in which a vehicle traveling at an initial lateral speed of 20 mph (32.2 km / h) is subjected to a side impact with a fixed pole,

[0008] – The IIHS Moving Deformable Barrier (MDB) side impact test involves a vehicle striking the side of a 1,500 kg (3,300 lb) deformable barrier moving at 50 km / h (31 mph).

[0009] These tests themselves are becoming more stringent, with more stringent requirements being placed on them, and the impact energy generated during testing is increasing.

[0010] The objective of the invention is to create a firewall assembly that exhibits exceptional crash safety performance. The invention also aims to create a vehicle with a firewall assembly according to the invention.

[0011] An object of the invention is also to create an engine shield assembly that has a lower weight than existing designs, thereby providing fuel savings in the case of internal combustion engines and an increase in driving range in the case of vehicles driven by electric motors.

[0012] Furthermore, the invention addresses the challenges of increasing productivity, reducing design complexity, and lowering vehicle production costs. The invention essentially provides a firewall assembly containing fewer parts than existing designs. Compared to existing designs, the design according to the invention can be manufactured and assembled in a very small number of steps. In addition to simplifying the manufacturing process, reducing costs, and increasing productivity, reducing the number of manufacturing steps also reduces the environmental impact of the production process and the overall CO2 emissions associated with vehicle manufacturing.

[0013] The objective of the invention is achieved by an assembled engine shield according to claim 1, optionally containing the features of claims 2-4, taken individually or in any possible combination. Another objective of the invention is achieved by a motor vehicle according to claim 5.

[0014] In the following description and claims, the terms indicating location and direction are defined according to generally accepted directions for the assembled vehicle.

[0015] In particular, the concepts of "top", "up", "upper", "over", "lower", "below", "under", etc. are defined according to the direction of the height of the vehicle. The concepts of "front", "rear", "forward", "backward", etc. are defined according to the longitudinal direction of the vehicle, i.e. the direction in which the vehicle moves in a straight line. The concepts of "left", "right", "transverse", etc. are defined according to the orientation parallel to the width of the vehicle. The concepts of "inner" and "outer" are defined according to the direction of the width of the vehicle: "inner" means closest to the central axis of the vehicle, i.e. closest to the inner side of the vehicle, while "outer" means located at a distance from the said central axis of the vehicle, in fact, near the outer side of the vehicle.The same applies to the concepts of "outer" and "central": the "outer" part is located closest to the vehicle's outer edge, while the "central" part is located closest to the vehicle's center. The concept of "horizontal" refers to the orientation of a plane containing the longitudinal and transverse directions. The concept of "vertical" refers to the orientation containing the vertical direction.

[0016] In the drawings, orientations and spatial references are represented using X, Y, and Z coordinates, where Z is the vehicle's vertical direction, X is the vehicle's longitudinal direction, and Y is the vehicle's transverse direction. This applies to each figure. When a figure is two-dimensional, the axis located outside the figure is indicated by a dot within a circle if it points toward the reader, and by a cross within a circle if it points away from the reader, according to generally accepted conventions.

[0017] The expressions "substantially parallel" and "substantially perpendicular" mean a direction that may deviate from the parallel or perpendicular direction by no more than 15°.

[0018] The term "steel sheet" refers to a flat sheet of steel. It has top and bottom faces, also called the upper and lower sides or top and bottom surfaces. The distance between these faces is called the sheet thickness. Thickness can be measured, for example, with a micrometer, the micrometer screw and the anvil of which are placed on the top and bottom surfaces. The thickness of a molded part can be measured in a similar manner.

[0019] The average thickness of a part or portion of a part means the total average thickness of the material from which the part is made after it is formed into a three-dimensional part from the original flat sheet.

[0020] Welded composite blanks are manufactured by assembling, for example by laser welding, multiple sheets or cut blanks of steel, known as sub-blanks, together. This is done to optimize the performance of the part in various areas, reduce the overall weight of the part, and reduce the overall cost of the part. The sub-blanks that make up the welded composite blanks can be assembled with or without overlapping. For example, they can be welded together by laser butt welding (without overlapping) or by resistance spot welding (with overlapping).

[0021] Unlike a welded composite workpiece, a solid workpiece is a workpiece that consists of one individual sub-workpiece without multiple sub-workpieces combined with each other.

[0022] Rolled composite blank is a blank having multiple sheet thicknesses obtained through a rolling operation in the steel sheet manufacturing process.

[0023] Tensile strength, yield strength, and elongation are measured according to ISO 6892-1, published in October 2009. Tensile test specimens are cut from flat areas. If necessary, small tensile test specimens are used to test the entire 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 clarity, the bending angle values ​​according to the invention are referred to a thickness of 1.5 mm. If the thickness is not equal to 1.5 mm, the bending angle value should be converted to a thickness of 1.5 mm using the following expression, where α1.5 is the bending angle converted to a thickness of 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 process that involves heating a steel blank or a preformed part made from a steel blank to a temperature at which the microstructure of the steel at least partially transforms into austenite, forming the blank or preformed part at high temperature by stamping it, and simultaneously quenching the formed part to obtain a microstructure having very high strength, with a possible additional redistribution or tempering step during heat treatment.

[0027] A multi-stage hot stamping process is a specific type of hot stamping process that includes at least one stamping step and at least two processing steps performed at a high temperature, above 300°C. For example, a multi-stage process may include an initial stamping operation and a subsequent hot trimming operation, so that the finished part exiting the hot stamping operation does not require subsequent trimming. For example, a multi-stage process may include multiple sequential stamping steps to produce parts with more complex shapes that could be achieved with a single stamping operation. For example, in a multi-stage process, parts are automatically transferred from one operation to another, such as using a transfer press.For example, the parts remain in the same tool, which is a universal tool and can perform various operations such as the first stamping operation and the subsequent trimming operation in the tool.

[0028] Fig. 1 shows a mechanical vehicle on which the installation location of the engine shield assembly is highlighted, a perspective view;

[0029] Fig. 2 – the assembled engine shield and the parts surrounding it, perspective view;

[0030] in Fig. 3 – the motor shield assembled according to the existing level of technology in a fully assembled state, perspective view;

[0031] Fig. 4 is a perspective view of a prior art engine shield assembly in which the individual parts connected together to form the engine shield assembly are shifted away from each other for clarity;

[0032] in Fig. 5 - the assembled motor shield according to the embodiment in a fully assembled state, perspective view;

[0033] Fig. 6 is a perspective view of an embodiment of the engine shield assembly in which the individual components connected together to form the engine shield assembly are shifted away from each other for clarity;

[0034] in Fig. 7A - the right part of the assembled motor shield according to the invention after cutting off the left part of the said assembled motor shield along plane AA in Fig. 5, perspective view;

[0035] in Fig. 7B - an assembled motor shield according to the invention, a schematic sectional view along plane AA in Fig. 5;

[0036] in Fig. 8A - a welded composite blank according to an embodiment used for producing the upper part of the engine shield according to the invention, a schematic view;

[0037] in Fig. 8B - a welded composite blank according to an embodiment used for producing the lower part of the engine shield according to the invention, a schematic view;

[0038] Fig. 9A – simulated crash test with a frontal impact on an overlap deformable barrier (ODB) at time t = 0 s, i.e. immediately before the vehicle impacts the barrier, perspective view;

[0039] Fig. 9B is the same as Fig. 9A, but the engine in the front engine compartment and the firewall assembly are shown so as to focus on the interaction of these components during a crash test;

[0040] in Fig. 10A, 10B and 11A, 11B – the course of the above-described process of crash test simulation for the time t = 0.085 s and t = 0.105 s.

[0041] With reference to Fig. 1 and 2, the passenger compartment 101 of the motor vehicle 100 is a space for accommodating the driver and passengers. The front engine compartment 102 of the vehicle 100 is a space located at the front of the vehicle and extends in the transverse direction across the width of the vehicle and in the longitudinal direction between the front bumper (not shown in the drawings) to the passenger compartment 101. Although said compartment is usually called the front engine compartment or the front engine compartment, in fact, in some vehicles it may not contain an engine or motor (for example, in a vehicle where the engine or motor is located in the rear, in the center, or directly attached to the wheels). In this case, said compartment can serve as a storage compartment, sometimes called a "front trunk."The engine compartment is usually closed by a hood located on top (not shown in the drawings).

[0042] For obvious safety reasons, the passenger compartment 101 must be protected in the event of an accident. The lower portion of the passenger compartment is bounded by floor panel 3, which extends transversely between the right and left lower side rails 6. In the case of an electric vehicle, the high-voltage battery housing is generally located beneath floor panel 3.

[0043] The firewall assembly 1 is a structural element that limits the passenger compartment 101 in the region of its lower front end and separates the passenger compartment from said front engine compartment 102. The firewall assembly 1 is also known as a heat-insulating wall or partition. It extends, in general, in the longitudinal and vertical direction between the floor panel 3 and the windshield (not shown in the figures). Between the firewall assembly 1 and the windshield, there may also be intermediate parts, for example, an upper partition 4, as shown in Fig. 2. Said upper partition, for example, is intended to support the windshield and / or hood hinges. In any case, said partition is not the main structural element of the vehicle and, in particular, does not play any role in the event of a frontal impact, in which the elements located inside the front engine compartment are thrown back and exert an impact on the firewall.

[0044] The engine shield 1 assembly occupies the entire space in the transverse direction of the vehicle between the right and left side lower rails 6 and between the right and left lower parts of the front pillars 2, as shown in Fig. 2. In general, it is attached to the following elements of the unpainted body:

[0045] – from the front to the right and left front side members 5 and to the right and left upper guides 7 of the wings,

[0046] – from the sides to the right and left side lower strapping beams 6 and to the right and left lower parts of the front posts 2,

[0047] – towards the rear of the vehicle to the floor panel 3, the nose 8 of the tunnel (which may be absent in the case of a vehicle with a fully electric drive) and the floor reinforcing elements that are attached to the floor panel 3 and are not shown in the drawings.

[0048] It should be noted that the above list of connecting elements is not limiting and is not necessarily complete, since its content depends on the selected design of the vehicle architecture. The invention relates, in particular, to the firewall assembly 1 and can be used with firewall assemblies connected to surrounding elements of various types. In any case, it is important that the firewall assembly 1 occupies a central position on the load path on the front of the vehicle, absorbing significant forces transmitted from structural elements ensuring frontal impact safety, such as, for example, the front side members 5 and the right and left upper guides 7 of the fenders.It also occupies a central position in the lateral load path of the front of the vehicle, for example, between the front of the side lower crossmembers 6 and a large portion of the front of the lower section of the front pillars 2. In fact, the firewall assembly is the main component of the front end of the vehicle and the side impact safety system, involved in absorbing, transmitting, and distributing impact energy during a collision. The firewall is also an important element for protecting against component penetration into the passenger compartment in the event of a frontal impact, when it is installed in the path between the engine in the front of the vehicle and the driver and front passengers. If the engine is not installed in the front engine compartment 102, it is installed directly between the passenger compartment and the element that impacts the vehicle.

[0049] Referring to Fig. 3, which shows an assembled firewall 1 according to the existing art, the firewall assembly typically has a generally curved shape, with its upper portion located further forward than its lower portion. Such a firewall typically has several openings communicating with the front engine compartment, for example, an opening 9 through which the pedal mechanism is inserted, or an opening 10 through which the steering column is inserted.

[0050] With reference to Fig. 4, which shows an assembled engine shield in an exploded view according to the existing art, said assembled engine shield according to the existing art is made of a plurality of individual parts assembled together, for example, by spot welding. In the example in Figs. 3 and 4, the assembled engine shield is assembled from 10 individual parts:

[0051] – right and left lower side parts 11,

[0052] – lower central part 12,

[0053] – right and left side brackets 13,

[0054] – reinforcing cross beam 14,

[0055] – right and left upper side parts 15,

[0056] – upper central part 16,

[0057] – upper right reinforcing part 17.

[0058] In the event of a frontal impact, the engine at the front of the vehicle is pushed rearward toward the passenger compartment, and the reinforcing cross member 14 plays an important role in resisting component penetration. The reinforcing cross member 14 has an omega-shaped shape and, when assembled with the remaining sub-sections, forms a hollow body extending in the transverse direction, effectively resisting component penetration. The right and left side brackets 13 also form hollow bodies on the sides of the firewall assembly, providing additional resistance to component penetration, especially in small overlap collisions in the width direction, which essentially concentrates energy on only one side of the firewall assembly.In addition, the side brackets 13 form strong assembly units with the lower parts of the front pillars and help to increase the collision resistance of vehicles in side impacts.

[0059] The right upper reinforcement part 17 is designed to provide additional rigidity in the area supporting the pedal mechanism.

[0060] The firewall assembly described above contains a large number of individual sub-parts, leading to a complex logistics and manufacturing chain. This also results in high costs, including tooling for the individual parts and their assembly. Furthermore, since these parts are joined together, for example by spot welding, they can become separated from each other under significant stress, such as impact stress or repeated fatigue stress over the life of the vehicle. Therefore, the presence of numerous sub-parts also creates potential weaknesses in the design.

[0061] With reference to Figs. 5 and 6, the firewall assembly according to the invention comprises, for comparison, only two parts, namely, the lower part 21 and the upper part 22 of the firewall. Both the lower part 21 and the upper part 22 of the firewall are made by forming a separate metal sheet. For example, at least one of said parts is manufactured by hot stamping a separate metal sheet. For example, at least one of said parts is manufactured by hot stamping through a multi-stage hot stamping process of a separate metal sheet. For example, at least one of said parts is manufactured by hot stamping a welded composite blank. For example, at least one of said parts is manufactured by stamping a rolled blank.

[0062] Referring to Fig. 6, the lower part 21 of the firewall includes a lower portion 211 and an overlapping portion 212 located in the upper section of the lower part 21 of the firewall. The upper part 22 of the firewall includes an upper portion 221 and an overlapping portion 222 located in the lower section of the upper part 22 of the firewall. After assembly, the lower and upper overlapping portions 212 and 222 of the firewall overlap each other (which corresponds to the concept of "overlapping"). The portion of the assembled firewall 1 in which the lower and upper portions of the firewall overlap each other is called the overlapping portion 12. On the other hand, after assembly of the firewall, the lower portion 211 of the lower part of the firewall and the upper portion 221 of the upper part of the firewall do not overlap each other.

[0063] With reference to Fig. 7B, which schematically shows a section of the firewall 1 assembled according to the invention, the overlapping section 12 comprises at least one flat overlapping region 122, in which the upper part 22 and the lower part 21 of the firewall are plane-parallel adjacent to each other. In other words, in at least one flat overlapping region 122 of the overlapping section 12, the overlapping section 212 of the lower part of the firewall and the overlapping section 222 of the upper part of the firewall have the same shape, as a result of which, after assembly, they are flatly adjacent to each other in said flat overlapping region 122. It is possible to assemble the upper part 22 and the lower part 21 of the firewall in at least one flat overlapping region 122, for example, by spot welding or laser welding.The flat overlap region 122 also provides the advantage of significantly increasing the resistance to component penetration because two layers of formed metal sheet are located in this region which jointly resist component penetration.

[0064] In a specific embodiment, as shown in Fig. 7A and 7B, the overlapping portion 12 also comprises at least one hollow portion 120, in which the overlapping portions 222 and 212 of the upper and lower parts of the firewall are located at a distance from each other in the longitudinal direction and define an internal volume between said overlapping portions 212 and 222. The presence of the hollow portion 120 has the advantage of increasing the overall rigidity of the firewall assembly 1, as well as increasing the resistance to penetration of components. In fact, the presence of the hollow portion 120 imparts rigidity to the firewall assembly and increases the resistance to deformation of said hollow portion.

[0065] In the drawings, the hollow section 120 is formed by designing substantially horizontal walls in the overlapping section 212 of the upper part of the firewall across the entire width of said section, as well as designing substantially horizontal walls on the side sections of the overlapping section 222 of the lower part of the firewall, wherein the central region of the overlapping section 222 of the lower part of the firewall remains substantially flat in the hollow section 120 and acts as a flat closing plate of the internal volume. Said design has the advantage of allowing the creation of larger hollow volumes on the sides of the firewall assembly, providing an increase in the resistance to penetration of components on the sides. This is particularly advantageous in the case of a frontal impact with a small overlap, during which the load is mainly applied only from one side of said part.

[0066] The hollow section 120 can be designed in various ways, for example, by using rounded bead-like shapes in the respective overlapping sections 222, 212 of the lower and / or upper parts of the engine shield.

[0067] In general, the amount of impact energy absorbed and the resistance to component penetration will be greater if the horizontal walls are designed in a metal sheet with the highest mechanical strength. For example, the amount of impact energy absorbed and the resistance to component penetration will be greater if the horizontal walls are designed in a metal sheet with the greatest thickness, the highest yield strength, or the largest product of the yield strength and the thickness of the metal sheet.

[0068] The design according to the invention significantly simplifies the inventive concept and the process of manufacturing the engine shield assembly by reducing the number of subparts. This, in turn, significantly reduces the number of subpart assembly points.

[0069] The reduction in the number of overlapping areas required to assemble the different sub-parts is due to the optimal choice of materials and also leads to a significant reduction in the weight of the assembled firewall.

[0070] Furthermore, the design according to the invention reproduces in a simplified form the basic safety features of modern design and, in particular, the reinforcement of the firewall assembly in its central section. Said reinforcement is provided, for example, by means of a reinforcing crossbar 14 of a modern design. In the design according to the invention, said reinforcement is provided by doubling the sheet thickness in section 12 and, if necessary, is increased by the presence of a hollow section 120 in the overlap section 12. The overlap section 12 of the present design according to the invention makes it possible to prevent the penetration of the engine from the front of the vehicle into the passenger compartment 101. It also makes it possible to increase the overall rigidity of the firewall and to withstand the effect of a transverse compressive load on the firewall in the event of a side impact.

[0071] In a specific embodiment, the engine shield assembly is manufactured by hot stamping of a steel sheet, and the blanks used to manufacture it comprise one of the following materials, either in the form of solid blanks or combined in the form of welded composite blanks:

[0072] – steel having the following composition in wt%: 0.06% ≤ C ≤ 0.1%, 1% ≤ Mn ≤ 2%, Si ≤ 0.5%, AI ≤ 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, the rest is iron and inevitable impurities resulting from the production process; Due to this composition range, the yield strength of the corresponding region after hot stamping is 700-950 MPa, the tensile strength is 950-1200 MPa, and the bending angle is greater than 75°; for example, this material is used in the region corresponding to the upper portion of the top of the engine shield because it absorbs energy without forming cracks, and this region does not need to withstand the penetration of components to the same extent as the overlapping portion 222 of the top of the engine shield;

[0073] – steel with a tensile strength after hot stamping of 1300–1650 MPa and a yield strength of 950–1250 MPa;

[0074] – steel with a tensile strength after hot stamping of 1300–1650 MPa, yield strength of 950–1250 MPa and a bending angle of greater than 75°;

[0075] – steel having the following composition in wt%: 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%, the rest is iron and inevitable impurities resulting from the production process; due to this composition range, the tensile strength of the corresponding region of the part after hot stamping is 1300-1650 MPa, and the yield strength is 950-1250 MPa; for example, this steel composition is used in the regions corresponding to the overlap section 12 of the engine shield assembly (i.e., for the steel from which the overlap sections 212, 222 of the upper and lower parts of the engine shield are made); in fact, this grade of steel has high performance in resisting the penetration of components;

[0076] – steel with a tensile strength after hardening under a press higher than 1800 MPa;

[0077] – steel having the following composition in wt.%: 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%, the rest is iron and inevitable impurities resulting from the manufacturing process; due to this composition range, the tensile strength of the corresponding area of ​​the engine shield assembly after hot stamping is above 1800 MPa; for example, this material is used in the overlap section 12 because it has excellent performance in resisting component penetration;

[0078] – steel having the following composition in % by weight: C: 0.15–0.25%, Mn: 0.5–1.8%, Si: 0.1–1.25%, Al: 0.01–0.1%, Cr: 0.1–1.0%, Ti: 0.01–0.1%, B: 0.001–0.004%, P ≤ 0.020%, S ≤ 0.010%, N ≤ 0.010% and containing, if necessary, one or more of the following elements in percentage by weight: Mo ≤ 0.40%, Nb ≤ 0.08%, Ca ≤ 0.1%, the balance being iron and unavoidable impurities resulting from melting; Due to this composition range, the tensile strength of the corresponding area of ​​the engine shield assembly after hot stamping is above 1350 MPa, and the bending angle is more than 70°;

[0079] – steel having the following composition in % by weight: C: 0.26–0.40%, Mn: 0.5–1.8%, Si: 0.1–1.25%, Al: 0.01–0.1%, Cr: 0.1–1.0%, Ti: 0.01–0.1%, B: 0.001–0.004%, P ≤ 0.020%, S ≤ 0.010%, N ≤ 0.010% and containing, if necessary, one or more of the following elements in percentage by weight: Ni ≤ 0.5%, Mo ≤ 0.40%, Nb ≤ 0.08%, Ca ≤ 0.1%, the balance being iron and inevitable impurities resulting from melting; due to this range of composition, the tensile strength of the corresponding area of ​​the engine shield assembly after hot stamping is above 1350 MPa, and the bending angle is greater than 70°;

[0080] – steel having the following composition in % by weight: C: 0.2–0.34%, Mn: 0.50–1.24%, Si: 0.5–2%, P ≤ 0.020%, S ≤ 0.010%, N ≤ 0.010% and containing, if necessary, one or more of the following elements in percentage by weight: Al ≤ 0.2%, Cr ≤ 0.8%, Nb ≤ 0.06%, Ti ≤ 0.06%, B ≤ 0.005%, Mo ≤ 0.35%, the balance being iron and inevitable impurities resulting from melting; Due to this composition range, the tensile strength of the corresponding area of ​​the engine shield assembly after hot stamping is equal to or higher than 1000 MPa, and the bending angle is greater than 55°;

[0081] – steel having the following composition in wt.%: C: 0.13–0.4%, Mn: 0.4–4.2%, Si: 0.1–2.5%, Cr ≤ 2%, Mo ≤ 0.65%, Nb ≤ 0.1%, Al ≤ 3.0%, Ti ≤ 0.1%, B ≤ 0.005%, P ≤ 0.025%, S ≤ 0.01%, N ≤ 0.01%, Ni ≤ 2.0%, Ca ≤ 0.1%, W ≤ 0.30%, V ≤ 0.1%, Cu ≤ 0.2% and confirming the following combination: 114 – 68*C – 18*Mn + 20*Si - 56*Cr - 60*Ni – 36*Al + 38*Mo + 79*Nb - 17691*B < 20, the rest is iron and inevitable impurities resulting from melting; for example, this composition is used in hot stamping of a part by a multi-stage process;

[0082] - Steel having an aluminum-based metallic coating applied to it; the term "aluminum-based" means a coating that contains at least 50% by weight of aluminum; for example, the metallic coating is an aluminum-based coating containing Si in an amount of 8-12% by weight; for example, the metallic coating is applied by dipping the base material into a molten metal bath; advantageously, applying the aluminum-based metallic coating eliminates the formation of surface scale during the heating step of the hot stamping process, which in turn enables the production of hot stamping parts without a subsequent sandblasting operation; in addition, the aluminum-based coating also provides anti-corrosion protection for the part during the use of the vehicle;

[0083] – steel with an applied metallic coating based on aluminum, containing 2.0-24.0% by weight of zinc, 1.1-12.0% by weight of silicon, if necessary, 0-8.0% by weight of magnesium and, if necessary, additional elements selected from Pb, Ni, Zr or Hf, wherein the weight content of each additional element is less than 0.3% by weight. the rest is aluminum and unavoidable impurities; as an advantage, the metallic coating of the specified type provides very good anti-corrosion protection of the part, as well as a good surface appearance after hot stamping.

[0084] In a specific embodiment, at least the upper or lower portion of the firewall is manufactured by hot stamping a welded blank welded by laser welding and comprising at least one sub-blank having an aluminum-based metallic coating, and said aluminum-coated sub-blanks are pre-prepared by ablation of at least a portion of the metallic coating on the edges to be welded. Advantageously, this allows for the removal of some of the aluminum present in the coating, which would otherwise contaminate the weld and impair its mechanical properties.

[0085] In a specific embodiment, at least one of the upper or lower parts of the firewall is manufactured by hot stamping a welded blank welded using laser welding and comprising at least one sub-blank having at least one side coated with an emissivity-enhancing top layer. Said emissivity-enhancing top layer is applied to the uppermost surface of said sub-blank. Said emissivity-enhancing top layer allows for the surface of said sub-blank to be obtained having a higher emissivity compared to the same sub-blank that is not coated with an emissivity-enhancing top layer. Said emissivity-enhancing top layer can be applied to either the upper or lower side of the sub-blank.Said emissivity-enhancing topcoat can be applied to both sides of said sub-workpiece. If said sub-workpiece contains a metallic coating, as described above, the emissivity-enhancing topcoat is applied over said metallic coating. In fact, for the emissivity-enhancing topcoat, to increase the surface emissivity, it is necessary to coat the outermost surface of the sub-workpiece. Advantageously, said emissivity-enhancing topcoat increases the heating rate of said sub-workpiece and, therefore, improves productivity during the heating stage of the hot stamping process.When using several sub-blanks with different thicknesses, the said top layer, which increases the emissivity, is advantageously applied to the sub-blanks having the greatest thickness in order to reduce the difference in heating time between the different sub-blanks and, therefore, to increase productivity, to increase the process window in the hot stamping process and to obtain, as a result, a finished part having uniform surface properties.

[0086] In a specific embodiment, the upper and lower parts of the engine shield are manufactured by hot stamping welded composite blanks, schematically shown in Fig. 8A and 8B, respectively. The steel grades and thicknesses will be described in detail with reference to the following tables (which can be compiled using the above-described embodiments in relation to the chemical composition of the steel grades).

[0087] Steel grade Yield strength (MPa) Tensile strength (MPa) Bending angle D1000 700-950 950-1200 At least 70° U1500 1300-1650 950-1250 -

[0088] D1000 steel has a low yield strength but a large bending angle. Therefore, it is more easily deformed and absorbs energy than U1500 steel. On the other hand, U1500 steel has superior penetration resistance compared to D1000 steel due to its higher strength.

[0089] With reference to Fig. 8A, the welded composite blank used to manufacture the upper portion 22 of the engine shield is composed of three sub-blanks 221A, 221B and 222, the steel grades and thicknesses of which are indicated below.

[0090] Sub-blank reference designation Steel grade Thickness 221A D1000 1.4 mm 221B D1000 1.0 mm 222A U1500 2.5 mm

[0091] Sub-blanks 221A and 221B correspond to the upper portion 221 of the upper part of the firewall after the element is formed. Sub-blank 222A, on the other hand, corresponds to the overlap portion 222 of the upper part of the firewall after the part is formed.

[0092] As described above, the function of the firewall assembly in preventing the penetration of components is mainly achieved by the overlapping section 12. Therefore, the sub-blank 222A according to the present embodiment is made of very high-strength D1500 steel having a large thickness of 2.5 mm. Furthermore, in the case of the present embodiment, after molding, the overlapping section 222 of the upper part of the firewall comprises substantially horizontal walls to form a hollow section 120 in the overlapping section 12. The selection of a very high strength and large thickness of the material of this section, as in the case of the present embodiment, is advantageous since it increases the rigidity and improves the performance of the firewall in resisting the penetration of components.

[0093] On the other hand, the upper section of the firewall can deform without cracking during a frontal impact to absorb energy. Therefore, D1000 grade steel was selected for sub-blanks 221A and 221B. Furthermore, since sub-blank 221A is located in the area where the pedal mechanism is inserted, thicker steel was selected for this sub-blank to increase the rigidity of this area.

[0094] Since the sub-workpiece 222A has a significantly larger thickness than the other sub-workpieces, it is worthwhile to apply the above-described emissivity-enhancing top layer to at least one side of the sub-workpiece 222A so that the heating rate of all areas of the welded composite workpiece in the austenitizing furnace is as uniform as possible.

[0095] Regarding the lower part 21 of the engine shield, the welded composite blank used to manufacture it is composed of five sub-blanks 212A, 212B, 211A, 211B and 21A, whose steel grades and thicknesses are as follows.

[0096] Sub-blank reference designation Steel grade Thickness 212A U1500 1.6 mm 212B U1500 1.6 mm 211A U1500 1.5 mm 211B U1500 1.5 mm 21A U1500 1.2 mm

[0097] Sub-blanks 212A and 212B correspond to the overlapping section 212 of the upper section of the lower part of the firewall after the part is formed. Conversely, sub-blanks 212A and 212B correspond to the lower section 211 of the lower part of the firewall after the part is formed. Sub-blank 21A covers both the overlapping section and the lower section after the part is formed.

[0098] As can be seen, the thickness of the material of the sub-blanks on the side faces of the part (212A, 212B, 211A, 211B) is greater than the thickness of the material of the central portion (21A). This ensures better resistance of the part in the event of a partial overlap collision, such as the above-described collisions simulated by the standard overlap deformable barrier (ODB) frontal impact or small overlap rigid barrier (SORB) impact tests. In addition, the blanks 212A, 212B corresponding to the sides of the overlap section have a greater thickness than those corresponding to the bottom section due to the need to ensure higher resistance to penetration of components in the overlap section.

[0099] The above-described embodiment makes it possible to significantly reduce the number of spot welds for assembling the firewall. For example, it makes it possible to reduce the number of spot welds from 158 spot welds in the firewall of the existing art (see Figs. 3 and 4) to 80 spot welds in the present embodiment (Figs. 5 and 6).

[0100] It also makes it possible to reduce the overall weight of the engine shield: the engine shield of the existing state of the art weighs 18.70 kg, while the design according to the invention weighs 17.34 kg, i.e. 7% less.

[0101] The inventors have found that it is possible to achieve the same safety performance during the Insurance Institute for Highway Safety (IIHS) ODB and SORB crash tests for a 18.70 kg engine shield according to the current state of the art and a 17.34 kg engine shield according to the invention. This demonstrates that the design according to the invention achieves a better compromise between safety performance and weight compared to the existing state of the art.

[0102] Figures 9A, B-11A, B show a simulated frontal impact crash test against an overlap deformable barrier (ODB) using the specific embodiment of the invention described above. During this test, the vehicle is impacted with only 40% of its width overlap against a deformable barrier traveling at a speed of 64.4 km / h (for clarity, the barrier is not shown in the drawings).

[0103] At the beginning of the test, shortly before the vehicle impacts the barrier (Fig. 9A and 9B), the engine 18 is located at a distance from the firewall assembly 1. After the barrier impacts the vehicle, it pushes the engine 18 backwards towards the passenger compartment, causing the engine to hit the firewall assembly 1 at a time of t = 0.085 s (Fig. 10A, 10B). The collision also affects the rotation of the engine 18 at an angle, as can be seen in the drawings. At a time of t = 0.105 s, the barrier reaches its maximum penetration depth (Fig. 11A and 11B). The simulation shows that the firewall assembly resists the penetration of the engine into the passenger compartment by, in particular, the overlap section 12. The upper and lower portions of the firewall deflect under the pressure applied by the engine, but there is no significant penetration and the overlap section 12 remains rigid.

Claims

1. An assembled firewall (1) for a motor vehicle (100) that occupies the entire space in the transverse direction of said motor vehicle between the right and left side lower rails (6) and between the right and left lower parts of the front pillars (2), wherein said firewall (1) assembled separates the front engine compartment (102) from the passenger compartment (101) and consists of a lower part (21) of the firewall and an upper part (22) of the firewall, wherein each of the said lower and upper parts (21, 22) of the engine shield is made by molding a separate metal sheet, said lower part (21) of the engine shield also comprises a lower section (211) and a covering section (212), said upper part (22) of the engine shield also comprises an upper section (221) and an overlapping section (222), after assembly to form the motor shield (1) as an assembly, the lower and upper parts (21, 22) of the motor shield overlap each other in the corresponding overlapping sections (212, 222) to form the overlapping section (12) of the motor shield as an assembly and do not overlap each other in the lower section (211) of the lower part of the motor shield and the upper section (221) of the upper part of the motor shield, the overlapping section (12) of the engine shield (1) as an assembly comprises at least one flat overlapping region (122) in which the lower part and the upper part (21, 22) of the engine shield are plane-parallel adjacent to each other; wherein the overlapping section (12) also comprises a hollow section (120) in which the overlapping sections (212, 222) of the lower and upper parts of the assembled engine shield are located at a distance from each other in the longitudinal direction to form a hollow volume between them.

2. An assembled engine shield (1) for a motor vehicle (100) according to claim 1, in which at least one part of the lower and upper parts (21, 22) of the engine shield is made by stamping a welded composite blank.

3. An assembled engine shield (1) for a motor vehicle (100) according to claim 1 or 2, in which at least one part of the lower and upper parts (21, 22) of the engine shield is made by hot stamping.

4. A motor vehicle (100) comprising a motor shield (1) assembled according to any one of paragraphs 1-3.

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