Side structure for autonomous vehicles

Abstract

This provides a side structure with a small number of parts, excellent safety performance, and optimal total weight. [Solution] A side structure (1) for an automobile, comprising an inner frame (11) and an outer frame (13), each forming a closing ring and having two openings corresponding to a front door and a rear door, wherein the inner frame (11) and the outer frame (13) are formed by hot stamping an inner frame blank and an outer frame blank, each being a single tailor-welded blank made of steel, and the inner frame (11) and the outer frame (13) are assembled to form a hollow volume between the two frames.

Description

Technical Field

[0001] The present invention relates to a side structure for an automobile.

Background Art

[0002] Automobile manufacturers are facing increasingly stringent requirements of reducing the vehicle weight to enhance the passive safety of the vehicle, minimizing greenhouse gas emissions in the case of an internal combustion engine, or increasing the driving range of the vehicle in the case of an electric vehicle, while keeping the production cost low and maintaining a high production speed.

[0003] The side structure of an automobile can be regarded as a side wall that separates vehicle occupants from the outside and protects the occupants from any intrusion in case of an accident. The side structure is also one of the main structural elements that connect the front collision management system and the rear collision management system, and is essential for the good transmission and absorption of the acting forces generated from the said systems.

[0004] Therefore, the side structure of an automobile is an important structural element of the vehicle, and contributes to the safety of the occupants in the case of a side impact, a front impact, and a rear impact, and also in the case of a rollover accident where the vehicle rolls over on its side and / or roof due to an accident or loss of control at a curb. Further, in the case of an electric vehicle where a battery pack is disposed under the vehicle floor panel, the side structure is also involved in protecting the battery pack from a side impact.

[0005] The side structure, which consists of a large number of individual parts, constitutes a significant mass of the vehicle body. The side structure also involves a costly manufacturing process, i.e., a number of shaping operations and assembly steps to obtain the completed structure.

[0006] An example of such a side structure in which the parts constituting the structure directly under the vehicle skin are made using a single tailor-welded blank is disclosed in Patent No. 5764667.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Patent No. 5764667 specification [Overview of the project] [Problems that the invention aims to solve]

[0008] The objective of this invention is to address the complex challenges of safety, weight reduction, and high productivity by providing a side structure with a small number of parts, excellent safety performance, and optimal total weight. [Means for solving the problem]

[0009] For this purpose, the present invention A side structure for an automobile comprising an inner frame and an outer frame, wherein the inner frame and the outer frame are each, The roof rail section, which is adjacent to the roof of the vehicle and corresponds to the upper part of the side structure, The rocker panel section, which is adjacent to the floor panel of the vehicle and corresponds to the bottom part of the side structure, The upper part of the A-pillar, which extends from the front end of the aforementioned roof rail section and is adjacent to the vehicle's windshield, corresponds to the side structure, The lower part of the A-pillar extends downward from the upper part of the A-pillar to the rocker panel, The upper part of the B-pillar extends downward in an upward direction from the roof rail portion between the front door and the rear door to the height of the windows of the front door and the rear door, The lower part of the B-pillar extends downward from the upper part of the B-pillar to the rocker panel, The lower part of the C-pillar extends upward in an elevation direction from the rear end of the rocker panel behind the rear door to the height of the rear door window, The upper part of the C-pillar extends upward from the lower part of the C-pillar to the roof rail portion, Equipped with, The inner frame and the outer frame each form a closing ring having two openings corresponding to the front door and the rear door. The inner frame and the outer frame are formed by hot stamping an inner frame blank and an outer frame blank, respectively, and the inner frame blank and the outer frame blank are each a single blank made of steel. The inner frame blank and outer frame blank are tailor-welded blanks composed of n inner sub-blanks and m outer sub-blanks, respectively, where n and m are integers of 2 or more. At least two inner subblanks have different thicknesses before hot stamping, and at least two inner subblanks have different tensile strengths after hot stamping. At least two outer subblanks have different thicknesses before hot stamping, and at least two outer subblanks have different tensile strengths after hot stamping. The inner frame and the outer frame are assembled to form a hollow volume between them. Regarding the side structure.

[0010] According to other optional features of the side structure according to the present invention, which are considered individually or in any possible technical combination, The inner frame blank and the outer frame blank each comprise at least one inner sub-blank and an outer sub-blank, which are coated with an aluminum-based metal coating.

[0011] The outer frame blank comprises at least one outer subblank, which is coated with an aluminum-based metal coating containing 2.0–24.0 wt% zinc, 1.1–12.0 wt% silicon, optionally 0–8.0 wt% magnesium, and optionally additional elements selected from Pb, Ni, Zr, or Hf, with each additional element having a weight content of less than 0.3 wt%, the remainder being aluminum and optionally unavoidable impurities.

[0012] The inner frame blank is composed of a series of n inner sub-blanks. Each inner sub-blank has a thickness ti before hot stamping and an ultimate tensile strength TSi after hot stamping. The product Pi = ti * TSi is calculated for each inner sub-blank. The inner frame blank has a minimum resistance inner sub-blank with a product Pmin, which is the minimum value of all products Pi of the n inner sub-blanks, and a maximum resistance inner sub-blank with a product Pmax, which is the maximum value of all products Pi of the n inner sub-blanks and, Pmax > 2 * Pmin.

[0013] The inner frame blank is composed of a series of m outer sub-blanks. Each outer sub-blank has a thickness ti before hot stamping and an ultimate tensile strength TSi after hot stamping. The product Pi = ti * TSi is calculated for each outer sub-blank. The outer frame blank (113) has a minimum resistance outer sub-blank with a product Pmin, which is the minimum value of all products Pi of the m outer sub-blanks, and a maximum resistance outer sub-blank with a product Pmax, which is the maximum value of all products Pi of the m outer sub-blanks, and, Pmax > 2 * Pmin.

[0014] The inner frame blank includes at least one inner sub-blank having an emissivity increasing top layer on at least one side .

[0015] The outer frame blank includes at least one outer sub-blank having an emissivity increasing top layer on at least one side.

[0016] The inner frame blank includes at least one inner sub-blank made of press-hardened steel having an ultimate tensile strength exceeding 1800 MPa after hot stamping.

[0017] The outer frame blank includes at least one outer sub - blank made of press - hardened steel having an ultimate tensile strength after hot stamping exceeding 1800 MPa.

[0018] The inner frame blank includes at least one inner sub - blank made of press - hardened steel having a yield strength after hot forming included in 700 - 950 MPa, an ultimate tensile strength after hot forming included in 950 - 1200 MPa, and a bending angle after hot forming exceeding 75°.

[0019] The outer frame blank includes at least one outer sub - blank made of press - hardened steel having a yield strength after hot forming included in 700 - 950 MPa, an ultimate tensile strength after hot forming included in 950 - 1200 MPa, and a bending angle after hot forming exceeding 75°.

[0020] The outer frame blank includes at least one metal patch.

[0021] At least one metal patch of the outer frame blank includes a radiation - emissivity increasing upper layer.

[0022] The outer frame blank includes at least one welding seam reinforcement patch, and the welding seam reinforcement patch is applied on a region with a welding seam.

[0023] At least one welding seam reinforcement patch of the outer frame blank includes a radiation - emissivity increasing upper layer.

[0024] The thickness of the inter - diffusion layer within the aluminum - based metal coating region of the inner frame is included in 3 - 15 microns.

[0025] The thickness of the inter - diffusion layer within the aluminum - based metal coating region of the outer frame is included in 3 - 15 microns.

[0026] Other aspects and advantages of the present invention will become apparent upon reading the following description given by way of example and made with reference to the accompanying drawings. [Brief explanation of the drawing]

[0027] [Figure 1] This is a first overall perspective view of the vehicle according to the present invention. [Figure 2] This is a second overall perspective view of the vehicle according to the present invention, in which the vehicle's outer shell is made transparent to allow viewing of the structural components underneath. [Figure 3] This is an exploded perspective view of the side structure according to the present invention. [Figure 4] This is a top view of a blank used to form the inner frame according to the present invention. [Figure 5] This is a top view of a blank used to form the outer frame according to the present invention. [Figure 6] This is a top view of the inner frame according to the present invention. [Figure 7] This is a top view of the outer frame according to the present invention. [Figure 8a] This is a schematic example of a cross-section of the side structure according to the present invention, with an arbitrary given plane perpendicular to the inner circumference, and the outline of the inner circumference is drawn by the dashed line 33 in Figure 2. [Figure 8b] This is a diagram of another schematic example of a cross-section of the side structure according to the present invention, with an arbitrary given plane perpendicular to the inner circumference, where the contour of the inner circumference is drawn by the dashed line 33 in Figure 2. [Modes for carrying out the invention]

[0028] In the following explanation, the terms “upper,” “lower,” “front,” “rear,” “transverse,” and “longitudinal” are defined according to the normal orientation of the vehicle on which it is mounted. More specifically, the terms “up,” “lower,” “up,” “down,” “bottom,” and “top” are defined according to the vehicle’s elevation angle; the terms “front,” “rear,” “forward,” “backward,” and “longitudinal” are defined according to the vehicle’s front / rear direction; and the term “transverse” is defined according to the vehicle’s width. The term “height” refers to the distance between two points, lines, surfaces, or volumes measured horizontally.

[0029] A steel blank refers to a flat steel sheet cut into any shape suitable for its use. The blank has a top and bottom surface, also referred to as the upper and bottom sides, or upper and bottom surfaces. The distance between these surfaces is called the thickness of the blank. The thickness can be measured, for example, using a micrometer, with the micrometer's spindle and anvil positioned on the top and bottom surfaces. Similarly, the thickness can also be measured on a molded part.

[0030] Yield strength, ultimate tensile strength, and uniform elongation and total elongation are measured in accordance with the ISO standard ISO 6892-1, published in October 2009.

[0031] 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 values ​​in this invention refer to a thickness of 1.5 mm. If the thickness is different from 1.5 mm, the bending angle values ​​need to be adjusted by the following calculation, however α 1.5 α is the bending angle at 1.5 mm, t is the thickness, and α t This is the bending angle relative to the thickness t.

[0032]

number

[0033] The bending angle of a component is a method of measuring its ability to resist deformation without forming cracks.

[0034] Emissivity is the relative power of a surface to radiate heat. It represents the ratio of the radiant energy emitted by a surface to the radiant energy emitted by a blackbody at the same temperature, and is a value between 0 and 1. The higher the emissivity of a blank's surface, the more heat the blank absorbs through radiation, and therefore, the easier it becomes to heat the blank using a radiant furnace.

[0035] Referring to Figures 1 and 2, the side structure 1 of the automobile 3 is described. The vehicle's outer skin is made transparent for clarity in Figure 2, and the side structure 1 is located beneath the outer skin. The automobile 3 can be any type of passenger car, such as a compact car, sedan, or sports car, and has at least a front door set and a rear door set. The side structure described above is essentially the same regardless of the vehicle category. Furthermore, the powertrain of the automobile can be a combustion engine, electric motor, fuel cell, or any type of hybrid system.

[0036] Figure 3 is an exploded view of the side structure 1 and body side outer 5 according to the present invention. The body side outer 5 constitutes the outer skin of the vehicle and essentially serves an aesthetic purpose, while the side structure 1 serves a structural purpose to ensure the collision resistance and overall rigidity of the body.

[0037] Referring to Figures 1 and 2, the side structure 1 comprises several parts separated by dashed lines in Figure 1, which are described below.

[0038] The roof rail section 1RR corresponds to the upper part of the side structure 1 adjacent to the roof 6. The roof rail section 1RR is connected to the roof cross beam 21 and plays an important role in the torsional rigidity of the vehicle and the vehicle structure's resistance to rollover.

[0039] A rocker panel section 1RP is located adjacent to the floor panel 20 of the vehicle and corresponds to the bottom portion of the side structure 1. The rocker panel section 1RP is connected laterally to the floor cross members 23. At its front end, the rocker panel section is longitudinally connected to the front cross member 15, possibly via an intermediate component. At its rear end, the rocker panel section is longitudinally connected to the rear cross member 25, possibly via an intermediate component. The rocker panel section 1RP is involved in preventing intrusion and absorbing energy in the event of a side collision that impacts the passenger compartment. Furthermore, because the rocker panel section is connected to the front side member 15 and the rear side member 25, it helps prevent intrusion and absorb energy in the event of a front or rear collision. The rocker panel section is particularly important in frontal or rear collisions affecting only a portion of the vehicle width, such as the Insurance Institute for Highway Safety (IIHS) Small Overlap Rigid Barrier (SORB) collision, where the vehicle collides with a rigid barrier moving at 64.4 km / h with an overlap of only 25% of the vehicle's width. In such configurations, only a portion of the frontal or rear collision management system is involved in resisting the collision. The side structure 1, connected to the front member 15 and rear member 25 by its rocker panel section 1RP, plays a crucial role in reinforcing the vehicle's resistance in such cases, picking up some of the collision energy, resisting intrusion, protecting occupants, and transferring collision energy to other structural members of the vehicle. In electric or hybrid vehicles with a battery pack (battery not shown) located beneath the floor panel 20, the rocker panel section 1RP also serves to protect the battery pack from intrusion in the case of a side impact and from deformation in the case of a frontal or rear impact.

[0040] The upper part 1AU of the A-pillar corresponds to the portion of the side structure 1 adjacent to the windshield 4. The upper part 1AU of the A-pillar plays an important role in resisting, absorbing, and transmitting collision energy in the event of a frontal impact, and is also important in ensuring the torsional rigidity of the entire vehicle.

[0041] The lower A-pillar 1AL extends downward from the upper A-pillar 1AU to the rocker panel 1RP. In the longitudinal direction, the lower A-pillar 1AL is connected to the front collision management system, such as the part commonly referred to as the shotgun 17. Therefore, as described above with respect to the rocker panel 1RP, the lower A-pillar plays an important role in transmitting, absorbing, and resisting collision energy in the event of a front collision, especially in the case of a small overlap collision. In the lateral direction, the lower A-pillar 1AL is connected to the lateral part, such as the dash panel 19, and helps to resist intrusion into the occupant compartment in the event of a side collision, as well as to transmit and absorb the forces generated by the side collision to the rest of the structure via the lateral part.

[0042] The upper part of the B-pillar 1BU extends downward in an upward direction from the roof rail portion 1RR between the front door 8 and the rear door 10 to the height of the windows of the front door 8 and the rear door 10. The upper part of the B-pillar 1BU plays an important role in preventing intrusion in the event of a side impact. In the upward direction, the upper part of the B-pillar is generally positioned at the height of the vital organs of the occupant (upper body), and therefore must effectively prevent intrusion into the occupant compartment in order to protect the life of the occupant.

[0043] The lower part of the B-pillar 1BL extends downward from the upper part 1BL of the B-pillar to the rocker panel portion 1RP. The lower part of the B-pillar 1BL is involved in preventing intrusion and absorbing energy in the event of a side collision that impacts the central and front end of the passenger compartment.

[0044] The lower C-pillar 1CL extends upward in an elevation direction from the rear end of the rocker panel portion 1RP behind the rear door 10 to the height of the window of the rear door 10. The lower C-pillar 1CL is involved in preventing intrusion and absorbing energy in the event of a side impact that strikes the rear of the passenger compartment. The lower C-pillar also helps to disperse and transfer collision energy to the rest of the vehicle structure in the event of a rear impact.

[0045] The upper C-pillar section 1CU extends upward from the lower C-pillar section 1CL to the roof rail section 1RR. The upper C-pillar section 1CU is involved in preventing intrusion and absorbing energy in the event of a side impact that strikes the rear of the passenger compartment. The lower C-pillar section also helps to disperse and transfer collision energy to the rest of the vehicle structure in the event of a rear impact.

[0046] The aforementioned side structure 1 forms a closing ring around the side of the vehicle 3, which has two openings corresponding to the front door 8 and the rear door 10.

[0047] Referring to Figure 3, the side structure 1 according to the present invention is formed by the association of an inner frame 11 and an outer frame 13. The inner frame 11 is located closest to the occupant compartment, and the outer frame 13 is located closest to the outside of the vehicle. Referring to Figures 6 and 7, the aforementioned side structure parts 1RR, 1AU, 1AL, 1RP, 1CL, 1CU, 1BL, and 1BU correspond, respectively, to the associated parts of the inner and outer frames 11RR, 11AU, 11AL, 11RP, 11CL, 11CU, 11BL, and 13RR, 13AU, 13AL, 13RP, 13CL, 13CU, 13BL, and 13BU separated by dashed lines in Figures 6 and 7. The inner frame 11 and the outer frame 13 each form a closing ring around the side of the vehicle 3, which has two openings corresponding to the front door 8 and the rear door 10.

[0048] Referring to Figures 4 and 5, the inner frame 11 and outer frame 13 are formed by punching out single steel blanks, inner frame blank 111 and outer frame blank 113, respectively. Using a single steel blank to produce each part offers several advantages in terms of manufacturing, structural resistance, and weight reduction. On the manufacturing side, this means there is only one forming process and no assembly process for individual sub-parts. This increases productivity and allows for higher geometric accuracy of the inner frame 11 and outer frame 13. In fact, the geometric tolerances of individual parts are summed up to calculate the geometric tolerance of the assembly. In this case, there are no additional geometric tolerances for individual parts. Furthermore, there are no assembly tolerance issues between individual parts. The use of a single blank also allows for improved part resistance, as there is no risk of fracture at the assembly joints between sub-parts in the event of impacts acting on the inner frame 11 and outer frame 13. Additionally, when loads are applied to the inner and outer frames, there is excellent energy transfer and diffusion within the inner and outer frames, ensuring optimal impact energy management. Furthermore, the fact that the inner frame 11 and the outer frame 13 are each made from a single component means that there is no overlapping area for assembly between the sub-components within the inner frame 11 and the outer frame 13 (this lack of overlap allows for weight reduction of the components).

[0049] Referring to Figures 4 and 5, the inner frame blank 111 and the outer frame blank 113 are steel Taylor welded blanks. Taylor welded blanks are made by assembling multiple steel blanks known as subblanks, for example by laser welding them together, in order to optimize the performance of the part in its various areas, reduce the overall weight of the part, and save on overall part costs. The inner frame blank 111 is made by assembling n inner subblanks IS1, IS2, ...ISi...ISn together, where n is an integer of 2 or more. Each inner subblank ISi and outer subblank OSi has a thickness before hot stamping and an ultimate tensile strength after hot stamping. A series of inner subblanks ISi comprises at least two subblanks having two different thicknesses. A series of inner subblanks ISi comprises at least two subblanks having two different tensile strengths after hot stamping. The outer frame blank 113 is made by assembling m outer subblanks OS1, OS2, ...OSi...OSm together, where m is an integer of 2 or more. A series of outer subblanks (OSi) comprises at least two subblanks having two different thicknesses. A series of outer subblanks (OSi) comprises at least two subblanks having two different tensile strengths after hot stamping.

[0050] The subblanks are assembled together by welding along the weld line 30. The weld line 30 is embodied by the black lines in Figures 4 and 5, which show specific embodiments of the inner frame blank 111 and the outer frame blank 113. The weld line is embodied by the white lines in Figures 6 and 7, which show specific embodiments of the inner frame 11 and the outer frame 13.

[0051] It should be understood that the positioning of the weld line 30 does not necessarily coincide with the various different parts of the inner frame 11 and outer frame 13 described above. In fact, vehicle designers place various subblanks having different thicknesses and different steel grades with different material strengths in appropriate areas to optimize the collision resistance, rigidity, and weight of the parts. This optimal placement of the weld line 30 does not necessarily correspond to the aforementioned boundaries between the parts of the inner frame 11 and the parts of the outer frame 13. For example, as shown in Figure 7, the roof rail section 13RR of the outer frame is made of material from three different subblanks.

[0052] Using Taylor welded blanks allows for the use of sub-blanks with different material thicknesses and strengths, thereby optimizing part performance. For example, by placing thicker, higher-strength material in areas requiring high resistance, such as within the blank for the upper 1BU of the side structure B-pillar, and thinner, lower-strength material in areas requiring less resistance, it is possible to design a part with optimal resistance while exhibiting an optimized overall weight. Furthermore, using Taylor welded blanks for the inner frame blank 111 and outer frame blank 113 reduces manufacturing scrap. When using monolithic blanks instead of Taylor welded blanks, the large openings in the inner frame blank 111 and outer frame blank 113 corresponding to doors 8 and 10 would need to be cut out from the blank and discarded. Using Taylor welded blanks allows for the use of nearly rectangular blanks, or complementary left / right shaped blanks, which are ideal for minimizing scrap to obtain good nesting when cutting the blanks from the steel coil. Minimizing scrap allows for minimizing the cost of the final part and simultaneously improving the environmental footprint of part production.

[0053] The inner frame 11 and outer frame 13 are manufactured by hot stamping the inner frame blank 111 and outer frame blank 113. Hot stamping is a forming technique that involves heating the blank to a temperature at which the steel's microstructure is transformed at least partially into austenite, forming the blank at high temperature by stamping it, and quenching the formed part to obtain a microstructure with very high strength. Hot stamping makes it possible to obtain parts with complex shapes and very high strength without springback. To bring about the aforementioned advantages of hot stamping, the material used is known as a press-hardened material, which has a chemical composition that allows it to form the desired hardened microstructure when subjected to the hot stamping process described above. It should be understood that the heat treatment the part undergoes includes not only the aforementioned thermal cycle of the hot stamping process itself, but also the subsequent paint-baking process performed after the part has been painted to bake the paint. The following mechanical properties of the hot-stamped part are measured after the paint-baking process, assuming that the paint-baking process is actually performed.

[0054] The inner frame 11 and outer frame 13 are large components that cover the entire length and height of the vehicle and have complex shapes. If there are springback issues after the parts are formed, there will be warping, distortion, and generally poor geometric tolerances that would make it difficult to assemble the parts as a single unit and install them into the rest of the vehicle. By using hot stamping, it is possible to manufacture the inner frame 11 and outer frame 13 with high geometric accuracy and with little to no springback issues.

[0055] By using hot-stamped Taylor weld blanks to form the inner frame 11 and outer frame 13, it is possible to design parts to have very important differences in thickness and strength across various regions of the part. Generally, a good indicator of resistance to penetration and the ability to absorb energy is considered to be the product of its ultimate tensile strength after hot stamping and its thickness before stamping.

[0056] Considering that the inner frame blank 111 is composed of a series of n inner subblanks IS1, IS2, ..., ISi, ... ISn, and each inner subblank ISi has a thickness ti before hot stamping and an ultimate tensile strength TSi after hot stamping, and the product Pi = ti * TSi is calculated for each inner subblank ISi, it is possible to select a minimum-resistance inner subblank ISmin having the minimum product Pmin of all inner subblanks ISi, and a maximum-resistance inner subblank ISmax having the maximum product Pmax of all inner subblanks ISi. In certain embodiments, the maximum product Pmax is significantly different from the minimum product Pmin. Advantageously, this means that the part has very different resistance levels in different regions of the part, and therefore has an optimal distribution of weight and resistance depending on the region of the part. For example, Pmax is advantageously at least twice as high as Pmin (in other words, Pmax > 2 * Pmin).

[0057] Considering that the outer frame blank 113 is composed of a series of m outer subblanks OS1, OS2, ..., OSi, ... OSm, and each outer subblank OSi has a thickness ti before hot stamping and an ultimate tensile strength TSi after hot stamping, and the product Pi = ti * TSi is calculated for each outer subblank OSi, it is possible to select a minimum-resistance outer subblank OSmin having the minimum product Pmin of all outer subblanks ISi, and a maximum-resistance outer subblank OSmax having the maximum product Pmax of all outer subblanks OSi. In certain embodiments, the maximum product Pmax is significantly different from the minimum product Pmin. Advantageously, this means that the part has very different resistance levels in different regions of the part, and therefore has an optimal distribution of weight and resistance depending on the region of the part. For example, Pmax is advantageously at least twice as high as Pmin (in other words, Pmax > 2 * Pmin).

[0058] For example, the inner frame 111 or the outer frame 113 comprises at least one subblank made of press-hardened steel having an ultimate tensile strength exceeding 1800 MPa after hot forming.

[0059] For example, the steel composition of the subblank contains, in weight percent, 0.24%≦C≦0.38%, 0.40%≦Mn≦3%, 0.10%≦Si≦0.70%, 0.015%≦Al≦0.070%, Cr≦2%, 0.25%≦Ni≦2%, 0.015%≦Ti≦0.10%, Nb≦0.060%, 0.0005%≦B≦0.0040%, 0.003%≦N≦0.010%, S≦0.005%, P≦0.025%, with the remainder being iron and unavoidable impurities resulting from processing. Within this composition range, the ultimate tensile strength of the part in the region corresponding to the subblank after press hardening is higher than 1800 MPa. For example, the subblank is made of Usibor(R)2000.

[0060] For example, the inner frame 111 or the outer frame 113 comprises at least one subblank made of press-hardened steel having a tensile strength of more than 1300 MPa after hot forming.

[0061] For example, the steel composition of the subblank contains, in weight percent, 0.20%≦C≦0.25%, 1.1%≦Mn≦1.4%, 0.15%≦Si≦0.35%, ≦Cr≦0.30%, 0.020%≦Ti≦0.060%, 0.020%≦Al≦0.060%, S≦0.005%, P≦0.025%, and 0.002%≦B≦0.004%, with the remainder being iron and unavoidable impurities resulting from processing. Within this composition range, the ultimate tensile strength of the part in the region corresponding to the subblank after press hardening falls within 1300MPa to 1650MPa, and the yield strength falls within 950MPa to 1250MPa. For example, the subblank is made of Usibor(R)1500.

[0062] For example, the inner frame 111 or outer frame 113 comprises at least one subblank having a steel composition containing, in weight percent, 0.06% ≤ C ≤ 0.1%, 1% ≤ Mn ≤ 2%, Si ≤ 0.5%, Al ≤ 0.1%, 0.02% ≤ Cr ≤ 0.1%, 0.02% ≤ Nb ≤ 0.1%, 0.0003% ≤ B ≤ 0.01%, N ≤ 0.01%, S ≤ 0.003%, P ≤ 0.020%, and less than 0.1% Cu, Ni, and Mo, with the remainder being iron and unavoidable impurities resulting from processing. Within this composition range, the yield strength of the part in the region corresponding to the subblank after press hardening is in the range of 700 to 950 MPa, the ultimate tensile strength is in the range of 950 to 1200 MPa, and the bending angle is greater than 75°. For example, the subblank is made of Ductibor(R) 1000.

[0063] For example, the inner frame 111 or outer frame 113 includes at least one subblank corresponding to a region of the final inner frame 11 or final outer frame 13 having an ultimate tensile strength in the range of 1350 MPa to 1650 MPa, a yield strength of 1000 MPa to 1300 MPa, and a bending angle greater than 70°.

[0064] For example, the inner frame 111 or outer frame 113 includes at least one subblank corresponding to a region of the final inner frame 11 or final outer frame 13 having an ultimate tensile strength in the range of 1500 MPa to 1800 MPa, a yield strength of 1250 MPa to 1500 MPa, and a bending angle greater than 70°.

[0065] Thanks to the use of tailor-welded blanks and hot stamping techniques, it is possible to obtain very high-strength inner and outer frames 11 and 13 that have optimized resistance within various areas of the parts and have very good geometric tolerances despite their large size and very high strength. The inner and outer frames 11 and 13 are assembled integrally around the periphery of their frames, including around the inner periphery of the openings corresponding to the doors 8, 10. Assembly is carried out, for example, by spot welding. The inner and outer frames are designed in such a shape that they form a hollow volume 7 between them when assembled, as shown in Figures 8a and 8b. Figures 8a and 8b show simplified cross-sections of the assembly of the inner and outer frames 11 and 13 along an arbitrary plane extending perpendicular to the inner circumference of the side structure, schematically defined by a dashed line labeled 33 in Figure 2. The hollow volume 7 provides excellent torsional rigidity to the side structure 1, which contributes to an increase in the overall rigidity of the vehicle body. This configuration can also effectively resist side impacts. The inertia provided by the hollow volume 7 results in good resistance to forces generated by side impacts. Furthermore, thanks to the isotropy of steel, the side structure 1 with the hollow volume 7 also has good resistance and good energy absorption capacity in the case of frontal or rear impacts, which applies longitudinal forces to the side structure 1. In this case, the fact that both the inner and outer frames are made from a single blank means that there is no risk of rupture between the sub-components that make up the assembly of the inner and outer frame structures. In fact, the longitudinal force of the impact will result in a shear force being exerted on the assembly point, which is an important configuration for the resistance of the assembly. Moreover, the inner frame 11 and the outer frame 13 are assembled together along the perimeter of the inner and outer frames, i.e., along a very wide area. This ensures good contact between the two frames and therefore also reduces the risk of delamination in the case of a frontal impact.

[0066] The design described above involves hot-stamping two tailor-welded blanks to form the inner frame 11 and outer frame 13, and assembling the inner and outer frames to form a hollow volume 7 that surrounds the entire perimeter of the side structure 1, which has the further advantage of providing very good collision resistance to the upper C-pillar 1CU and lower C-pillar 1CL. This makes it possible to better protect rear-seat occupants of the vehicle. It is also anticipated that safety regulations are constantly evolving towards stricter requirements. While resistance in the C-pillar area is not a major focus of safety testing today, it may become so in the near future.

[0067] In certain embodiments, reinforcing members 29 are provided within the hollow volume 7 in areas where additional rigidity or resistance to impact is required. The reinforcing members 29 can have different cross-sections, as shown in the schematic examples in Figures 8a and 8b. For example, the reinforcing member 29 may have a general U-shape, with its bottom attached to the outermost wall of the outer frame 13 (Figure 8b). In another example, the reinforcing member 29 may have a general omega shape, with its bottom portion used as a flange for attaching the reinforcing member to the outermost wall of the outer frame 13 (Figure 8a). The reinforcing member 29 may be attached to the outer frame 13, for example, by spot welding.

[0068] In certain embodiments, the inner frame blank 111 and / or outer frame blank 113 comprises at least one sub-blank coated with an aluminum-based metal coating. "Aluminum-based" means a coating containing at least 50% aluminum by weight. For example, the metal coating is an aluminum-based coating containing 8-12% Si by weight. For example, the metal coating is applied by immersing the substrate in a molten metal bath. Advantageously, applying an aluminum-based metal coating to the inner frame 111 or outer frame 113 avoids the formation of surface scale during the heating step of the hot stamping process, thereby enabling the production of parts by hot stamping without subsequent sandblasting. Furthermore, the aluminum-based coating also provides corrosion protection to parts in use on a vehicle.

[0069] In certain embodiments, the inner frame 111 and / or outer frame 113 consist of at least one subblank, which is coated with an aluminum-based metal coating containing 2.0–24.0 wt% zinc, 1.1–12.0 wt% silicon, optionally 0–8.0 wt% magnesium, and optionally additional elements selected from Pb, Ni, Zr, or Hf, with each additional element having a weight content of less than 0.3 wt%, the remainder being aluminum and optionally unavoidable impurities. Advantageously, this type of metal coating provides very good corrosion protection on the part and results in a good surface appearance after hot stamping.

[0070] Laser welding can be used to manufacture the above-mentioned tailor weld blanks having an aluminum-based coating on at least one of the subblanks of the above frame. It is possible to use subblanks that have been pre-prepared by removing a portion of the metal coating from the edge to be welded. Advantageously, this removes the portion of aluminum present in the coating that would contaminate the weld seam and degrade its mechanical properties.

[0071] In certain embodiments, the inner frame 111 and / or outer frame 113 comprises at least one subblank having an emissivity-enhancing upper layer on at least one side. The emissivity-enhancing upper layer is applied to the outermost surface of the subblank. The emissivity-enhancing upper layer allows the surface of the subblank to have a higher emissivity compared to the same subblank not covered with the emissivity-enhancing upper layer. The emissivity-enhancing upper layer can be applied to either the upper or bottom side of the subblank. The emissivity-enhancing upper layer can also be applied to both sides of the subblank.

[0072] If the subblank has a metal coating as described above, the emissivity-enhancing upper layer is applied on top of the metal coating. In fact, for the emissivity-enhancing upper layer to increase the surface emissivity, this layer must cover the outermost surface of the subblank.

[0073] Advantageously, the emissivity-increasing upper layer increases the heating rate of the subblank, thus improving the productivity of the heating process in the hot stamping process.

[0074] In certain embodiments, the inner subblanks ISi and outer subblanks OSi are sorted in increasing order of thickness. The emissivity-increasing top layer is applied to at least one side of the subblank having the maximum thickness. In certain embodiments, the emissivity-increasing top layer is applied to at least one side of the subblank having the maximum thickness and the subblank having a thickness slightly thinner than the maximum thickness. In certain embodiments, the emissivity-increasing top layer is applied to x subblanks having the maximum thickness, where x is an integer greater than or equal to 1. Advantageously, by applying the emissivity-increasing top layer to a set of thicker subblanks, it is possible to achieve a more uniform heating rate during the heating step of the hot stamping process between thicker and thinner subblanks. In fact, thinner subblanks heat up more quickly and naturally than thicker subblanks because they require less energy to reach the same temperature. By targeting the thicker subblanks with the emissivity-increasing top layer, it is possible to reduce the difference in heating rates between blanks of different thicknesses, and thus it is possible to achieve a more uniform heating rate between thicker and thinner subblanks. Furthermore, by targeting thicker subblanks with an emissivity-enhancing top layer, it is possible to increase the size of the process window in the heating phase of the hot stamping process for the blank. When hot stamping large parts with large thickness differences, one concern is the large differences in the process windows (including heating time and heating temperature, among other parameters) required to achieve the desired microstructure and coating properties of different subblanks. The process window required to achieve the desired properties across the entire blank is the intersection between the respective process windows of the individual subblanks. By applying an emissivity-enhancing top layer onto thicker subblanks, it is possible to bring the respective process windows of the individual subblanks closer together, thereby increasing the size of the intersection between the process windows of all subblanks, i.e., increasing the overall process window of the tailor-welded blank.

[0075] In certain embodiments, the emissivity-enhancing upper layer has a thickness of 2 to 30 microns. In certain embodiments, the emissivity-enhancing upper layer is composed of a polymer that does not contain silicon, contains more than 1% by weight of nitrogen, and contains 3 to 30% by weight of carbon pigment.

[0076] In certain embodiments, the outer frame blank 113 further comprises at least one metal patch 31, as shown in Figure 5, to locally increase the strength of the part. In certain embodiments, the patch 31 is attached by spot welding. In certain embodiments, the patch 31 is attached by laser welding. The patch 31 is applied to areas that need to be reinforced, for example, due to the presence of a door hinge or due to mechanical problems such as folding of the part detected during crash testing.

[0077] Generally speaking, Patch 31 offers the advantage of providing very localized reinforcement on larger parts, thereby further optimizing the strength and thickness distribution of the entire Taylor weld blank while keeping the overall weight and cost of the part low.

[0078] Patch 31 is made, for example, from press-hardened steel. Patch 31 is coated, for example, with an aluminum-based metal coating.

[0079] In certain embodiments, patch 31 is covered with an emissivity-increasing upper layer to increase the heating rate and thus reduce the difference in heating rates within the region of patch 31 associated with the excessive thickness of patch 31, as described above.

[0080] In certain embodiments, the patch is applied to an area that includes a portion of the weld seam 30. As shown in the B-pillar section of Figure 5, the patch is referred to as a weld seam reinforcement patch 32. This type of patch 32 has exactly the same features as described above and optional features. This type of patch 32 reinforces the weld seam 30. The weld seam 30 is an area where a discontinuity exists between two subblanks, and this discontinuity can cause local inertial fluctuations, potentially leading to a plastic hinge-type collapse when subjected to high loads generated by a collision. By reinforcing the weld seam 30 with the weld seam reinforcement patch 32, such a plastic hinge phenomenon can be prevented. The weld seam reinforcement patch 32 is attached, for example, by welding it to the outer frame 13. In certain embodiments, the attachment point between the weld seam reinforcement patch 32 and the outer frame 13 is not within the area of ​​the weld seam 30 so as not to interfere with the mechanical properties of the weld seam 30.

[0081] When press-hardened steel coated with an aluminum-based metal coating is used for the inner frame blank 111 or outer frame blank 113, the hot stamping process induces the formation of an interdiffusion layer between the steel and the metal coating on the hot-formed part. The interdiffusion layer is the result of high-temperature cross-diffusion of Fe from the steel toward the metal coating and Al from the coating toward the steel. The thickness of the interdiffusion layer has been shown to correlate with further in-use properties of the part, such as the ability of the part to be successfully assembled to the rest of the body by spot welding. In particular, hot-formed parts with an interdiffusion layer thickness between 3 and 15 microns have been shown to have good in-use properties. More preferably, hot-formed parts with an interdiffusion layer thickness between 3 and 10 microns have been shown to have excellent in-use properties.

[0082] In certain embodiments, the thickness of the interdiffusion layer within the aluminum-based metal coating area of ​​the inner frame 11 is between 3 microns and 15 microns. In certain embodiments, the thickness of the interdiffusion layer within the aluminum-based metal coating area of ​​the inner frame 11 is between 3 microns and 10 microns. In certain embodiments, the thickness of the interdiffusion layer within the aluminum-based metal coating area of ​​the outer frame 13 is between 3 microns and 15 microns. In certain embodiments, the thickness of the interdiffusion layer within the aluminum-based metal coating area of ​​the outer frame 13 is between 3 microns and 10 microns.

[0083] The present invention also relates to a process for producing the above-described side structure 1 and assembling it to the rest of the vehicle body.

[0084] In a particular embodiment, the process consists of the following steps (steps A, B, C, and D are not listed in a specific order): A / A process of providing an inner frame blank 111, B / Process to provide the outer frame blank 113, C / The process of forming the inner frame 11 by hot stamping the inner frame blank 111, D / A process of forming the outer frame 13 by hot stamping the outer frame blank 113, E / Steps to assemble the inner frame 11 and the outer frame 13 to form the side structure 1, F / The process of attaching side structure 1 to the vehicle body, G / The process of attaching the body side outer 5 to the already assembled side structure 1, It consists of.

[0085] Optionally, the process further includes a step of attaching a reinforcing member 29 to the outer frame 13 between step D and step E.

[0086] In a particular embodiment, the process consists of the following steps (steps A, B, C, and D are not listed in a specific order): A / A process of providing an inner frame blank 111, B / Process to provide the outer frame blank 113, C / The process of forming the inner frame 11 by hot stamping the inner frame blank 111, D / A process of forming the outer frame 13 by hot stamping the outer frame blank 113, The process of attaching the inner frame 11 to the vehicle body. E / Step of attaching the outer frame 13 to form the side structure 1, G / The process of attaching the body side outer 5 to the already assembled side structure 1, It consists of.

[0087] Optionally, the process further includes a step of attaching a reinforcing member 29 to the outer frame 13 between step D and step E.

Claims

1. A side structure (1) for an automobile (3) comprising an inner frame (11) and an outer frame (13), wherein the inner frame (11) and the outer frame (13) are each The roof rail section (11RR, 13RR) is adjacent to the roof (6) of the vehicle and corresponds to the upper part of the side structure (1), Rocker panel sections (11RP, 13RP) that are adjacent to the floor panel (20) of the vehicle and correspond to the bottom portion of the side structure (1), The upper part of the A-pillar (11AU, 13AU) extends from the front end of the roof rail section (11RR, 13RR) and is adjacent to the vehicle's windshield (4), and corresponds to the part of the side structure (1) that is adjacent to the vehicle's windshield (4), The lower part of the A-pillar (11AL, 13AL) extends downward from the upper part of the A-pillar (11AU, 13AU) to the rocker panel part (11RP, 13RP), The upper part of the B-pillar (11BU, 13BU) extends downward in an upward direction from the roof rail portion (11RR, 13RR) between the front door (8) and the rear door (10) to the height of the windows of the front door (8) and the rear door (10), The lower part of the B-pillar (11BL, 13BL) extends downward from the upper part of the B-pillar (11BU, 13BU) to the rocker panel section (11RP, 13RP), The lower part of the C-pillar (11CL, 13CL) extends upward in an elevation direction from the rear end of the rocker panel portion (11RP, 13RP) behind the rear door (10) to the height of the window of the rear door (10), The upper part of the C-pillar (11CU, 13CU) extends upward from the lower part of the C-pillar (11CL, 13CL) to the roof rail section (11RR, 13RR), Equipped with, The inner frame (11) and the outer frame (13) each form a closing ring having two openings corresponding to the front door (8) and the rear door (10). The inner frame (11) and the outer frame (13) are formed by hot stamping an inner frame blank (111) and an outer frame blank (113), respectively, and the inner frame blank (111) and the outer frame blank (113) are each single blanks made of steel. The inner frame blank (111) and outer frame blank (113) are tailor weld blanks composed of n inner subblanks (IS1, IS2, ..., ISi, ... ISn) and m outer subblanks (OS1, OS2, ..., OSi, ... OSm), respectively, where n and m are integers of 2 or more. The inner subblanks (IS1, IS2, ..., ISi, ... ISn) comprise at least two inner subblanks having different thicknesses before hot stamping, and at least two inner subblanks having different tensile strengths after hot stamping. The outer subblanks (OS1, OS2, ..., OSi, ... OSm) comprise at least two outer subblanks having different thicknesses before hot stamping, and at least two outer subblanks having different tensile strengths after hot stamping. The inner frame (11) and the outer frame (13) are assembled to form a hollow volume (7) between the two frames. Side structure (1).

2. The side structure (1) according to claim 1, wherein the inner frame blank (111) and the outer frame blank (113) each comprise at least one inner sub-blank (ISi) and an outer sub-blank (OSi) covered with an aluminum-based metal coating.

3. The side structure (1) according to claim 1 or 2, wherein the outer frame blank (113) comprises at least one outer subblank (OSi), the outer subblank being coated with an aluminum-based metal coating containing 2.0 to 24.0 wt% zinc, 1.1 to 12.0 wt% silicon, optionally 0 to 8.0 wt% magnesium, and optionally additional elements selected from Pb, Ni, Zr, or Hf, the weight content of each additional element being less than 0.3 wt%, with the remainder being aluminum and optionally unavoidable impurities.

4. The inner frame blank (111) is composed of a series of n inner subblanks (IS1, IS2, ..., ISi, ... ISn), each inner subblank (ISi) has a thickness ti before hot stamping and an ultimate tensile strength TSi after hot stamping, and the product Pi = ti * TSi is calculated for each inner subblank (ISi), and the inner frame blank (111) is, A minimum resistance inner subblank (ISmin) having a product Pmin which is the minimum value of the product Pi of all the n inner subblanks, A maximum-resistance inner subblank (ISmax) having a product Pmax which is the maximum value of the total product Pi of the n inner subblanks, Equipped with, Pmax > 2 * Pmin. The side structure (1) according to any one of claims 1 to 3.

5. The outer frame blank (113) is composed of a series of m outer subblanks (OS1, OS2, ..., OSi, ... OSm), each outer subblank (OSi) having a thickness ti before hot stamping and an ultimate tensile strength TSi after hot stamping, and the product Pi = ti * TSi is calculated for each outer subblank (OSi), and the outer frame blank (113) is, A minimum resistance outer subblank (OSmin) having a product Pmin which is the minimum value of the product Pi of all m outer subblanks, A maximum-resistance outer subblank (OSmax) having a product Pmax which is the maximum value of the total product Pi of the m outer subblanks, Equipped with, Pmax > 2 * Pmin. The side structure (1) according to any one of claims 1 to 3.

6. The side structure (1) according to any one of claims 1 to 5, wherein the inner frame blank (111) comprises at least one inner sub-blank (ISi) having an emissivity increasing upper layer on at least one side.

7. The side structure (1) according to any one of claims 1 to 5, wherein the outer frame blank (113) comprises at least one outer sub-blank (OSi) having an emissivity increasing upper layer on at least one side.

8. The side structure (1) according to any one of claims 1 to 7, wherein the inner frame blank (111) comprises at least one inner sub-blank (ISi) made of press-hardened steel having an ultimate tensile strength after hot stamping of more than 1800 MPa.

9. The side structure (1) according to any one of claims 1 to 8, wherein the outer frame blank (113) comprises at least one outer subblank (OSi) made of press-hardened steel having an ultimate tensile strength after hot stamping of more than 1800 MPa.

10. The side structure (1) according to any one of claims 1 to 9, wherein the inner frame blank (111) comprises at least one inner sub-blank (ISi) made of press-hardened steel having a yield strength after hot forming in the range of 700 to 950 MPa, an ultimate tensile strength after hot forming in the range of 950 to 1200 MPa, and a bending angle after hot forming greater than 75°.

11. The side structure (1) according to any one of claims 1 to 10, wherein the outer frame blank (113) comprises at least one outer subblank (OSi) made of press-hardened steel having a yield strength after hot forming in the range of 700 to 950 MPa, an ultimate tensile strength after hot forming in the range of 950 to 1200 MPa, and a bending angle after hot forming greater than 75°.

12. The side structure (1) according to any one of claims 1 to 11, wherein the outer frame blank (113) comprises at least one metal patch (31).

13. The side structure (1) according to claim 12, wherein at least one metal patch (31) of the outer frame blank (113) comprises an emissivity increasing upper layer.

14. The side structure (1) according to any one of claims 1 to 13, wherein the outer frame blank (113) comprises at least one weld seam reinforcement patch (32), the weld seam reinforcement patch (32) is applied over an area comprising a weld seam (30).

15. The side structure (1) according to claim 14, wherein at least one weld seam reinforcement patch (32) of the outer frame blank (113) comprises an emissivity increasing upper layer.

16. The side structure (1) according to any one of claims 1 to 15, wherein the thickness of the interdiffusion layer within the aluminum-based metal coating region of the inner frame (11) is between 3 microns and 15 microns.

17. The side structure (1) according to any one of claims 1 to 16, wherein the thickness of the interdiffusion layer within the aluminum-based metal coating region of the outer frame (13) is between 3 microns and 15 microns.

Images