Motor vehicle bending beam

Abstract

A vehicle bending beam according to the invention comprises a base body 2 made of hardenable steel and a reinforcing plate 3 made of hardenable steel joined to the base body 2. The base body 2 and the reinforcing plate 3 are formed together, the base body 2 having a longitudinal section 4 which has two legs 7 and a web 8 connecting the legs 7. The reinforcing plate 3 is arranged in the longitudinal section 4 and abuts at least one leg-side edge section 10 against a leg 7. According to the invention, the edge section 10 of the reinforcing plate 3 extends along a step 13 formed in the leg 7. This design improves the forming process and the optional in-mold hardening.

Description

[0001] The invention relates to a motor vehicle bending beam according to the features in the preamble of claim 1 and a motor vehicle with such a motor vehicle bending beam.

[0002] Bending beams of the type used in motor vehicles according to the invention are, in particular, B-pillars or bumpers or bumper cross members, but also generally bending beams with a hat-shaped, U-shaped, or V-shaped cross-section. Such bending beams are subject to the highest requirements regarding their strength and bending stiffness. They should also ensure good crash performance.

[0003] High-strength steels are used to manufacture automotive bending beams, in particular martensitic steels, multiphase steels, or manganese-boron steels. For the latter, hot forming is considered state of the art. Hot forming is a process for the hot forming of steel sheets, also known as press hardening. In hot forming, a sheet of manganese-boron steel is heated to a temperature above the specific austenitizing temperature of the material, placed in a forming die, and hot formed into the component, cooling during the forming process. Clamped in the forming die, the bending beams are hardened by the cooling process.

[0004] It is also common practice in automotive manufacturing to locally reinforce bending beams with one or more reinforcing plates. Such a reinforcing plate is technically called a patch. A method for manufacturing locally reinforced sheet metal forming parts is considered state of the art according to DE 100 49 660 B4.

[0005] The base body and the reinforcing plate are made of hardenable steel. The reinforcing plate and the base body are joined together by a metallurgical bond. To manufacture the bending beam, the reinforcing plate is typically pre-assembled to the base plate, which forms the base body, using steel sheet, for example, by spot welding. Subsequently, the base plate and the reinforcing plate are hot-formed and press-hardened together to create the three-dimensional shape of the bending beam.

[0006] When a reinforcing plate is positioned on the outside of the base body, a kind of undercut can occur at the transition between the lateral edges of the reinforcing plate and the legs of the base body during forming. This results in the upper tool not making full contact with the components. This non-contact area can negatively affect hardening during hot forming and press hardening, and in particular, it makes forming a radius between the legs and an outwardly directed flange adjoining a leg difficult or impossible. This affects the functionality and quality of the automotive bending beam. It can also adversely affect the deformation behavior of the bending beam in a crash.

[0007] German patent DE-10 2011 120 519 A1 discloses a B-pillar for a motor vehicle. The B-pillar features a reinforcement consisting of a strengthening structure and a stiffening structure. The stiffening structure is connected to the strengthening structure to stiffen the latter against a side impact of the vehicle. The strengthening structure is said to be made of weldable non-boron steel, and the stiffening structure of hardened boron steel.

[0008] US 2005 / 0189790 A1 describes a two-piece side frame for a motor vehicle with a one-piece inner sheet and a one-piece outer sheet.

[0009] A B-pillar reinforced by a reinforcing plate is revealed. Fluid forming techniques, such as quick plastic forming (QPF) or superplastic forming (SPF), and sheet metal hydroforming processes are suggested.

[0010] Furthermore, JP 2020-121 690 A shows a B-pillar which has a base body reinforced by a reinforcing plate, wherein the base body and the reinforcing plate are formed together.

[0011] Starting from the prior art, the invention is based on the objective of demonstrating a functionally and qualitatively improved motor vehicle bending beam with good crash performance.

[0012] According to the invention, the solution to this problem consists of a motor vehicle bending beam according to the features of claim 1.

[0013] Advantageous embodiments of the vehicle bending beam according to the invention are the subject of the dependent claims.

[0014] A bending member for motor vehicles according to the invention is, in particular, a vehicle pillar, especially a B-pillar, or a bumper crossmember. The bending member can also be a component of a vehicle's door ring system. In a vehicle door ring, bending-relevant sections in the vehicle's longitudinal axis, transverse axis, and / or vertical axis can be formed by bending members according to the invention. The door ring can be made in one piece, with bending-relevant sections formed by a bending member designed according to the invention.

[0015] The automotive bending beam has a base body that is locally reinforced by a reinforcing plate. Both the base body and the reinforcing plate are made of a hardenable hot-forming steel. The base body and the reinforcing plate can be made of the same steel or steel alloy. However, the steels used for the base body and the reinforcing plate can also be different. The initial blanks for the base body and the reinforcing plate are flat.

[0016] The flat reinforcing plate is fixed to the base plate, for example by spot welding, specifically at the point where it will perform its reinforcing function in the finished bending beam. The base plate and the reinforcing plate are then formed and press-hardened together in a press tool. After forming and / or press hardening, the reinforcing plate can be joined to the base body. This is also preferably done by welding.

[0017] The base body of the automotive bending beam has a longitudinal section with a hat-, U-, or V-shaped cross-section. This longitudinal section has two legs and a web connecting them. The reinforcing plate is arranged within this longitudinal section and is shaped to match the cross-sectional configuration of the reinforcing plate's longitudinal section. When the automotive bending beam is installed in a vehicle, the reinforcing plate is attached to the outside of the bending beam. The reinforcing plate rests against at least one leg-side edge section. Specifically, the reinforcing plate overlaps the base body within this longitudinal section. Accordingly, the reinforcing plate also has a hat-, U-, or V-shaped cross-section. In this configuration, the reinforcing plate has a back surface that rests fully against the web.A leg-side edge section adjoins the back of the reinforcement plate on each side.

[0018] According to the invention, at least one edge section extends along a step formed in the leg against which the edge section abuts.

[0019] Preferably, a step extending in the longitudinal direction of the length section is provided in each leg, along which the associated edge section extends.

[0020] The solution according to the invention provides a remedy for the undercut problem that occurs at the transition between the end of the reinforcing plate along the edge section and the base body. The automotive bending beam according to the invention is functionally and qualitatively improved and exhibits advantageous crash performance.

[0021] During the forming process, the outer tool is in full contact with the reinforcing plate and the lower leg section adjoining the step. This allows the forming forces to act evenly. The forming process is improved, as is the hardening process in the case of press hardening, which is significantly more efficient and uniform. Undercuts are avoided.

[0022] The base body and the reinforcing plate have a tensile strength Rm of greater than or equal to (≥) 1,000 MPa. The base body and the reinforcing plate are made of a hardenable steel, in particular a manganese-boron alloyed hot-forming steel.

[0023] The tensile strength of the vehicle bending beam is greater than or equal to (≥) 1,000 MPa.

[0024] The invention provides that the base plate and the reinforcing sheet are made of hardenable steel and are hot-formed and press-hardened together in a press tool. The components undergo a press hardening process.

[0025] The stage(s) provided according to the invention are produced during the forming process. The stages are produced simultaneously with the hot forming or the cold forming, preferably in the same forming stage.

[0026] The reinforcing plate is flush with the outer surface of the step at the edge section. The transition between the outer surface of the reinforcing plate and the adjacent outer surface of the base body is seamless.

[0027] The step has a step height which is greater than or equal to (≥) the thickness of the reinforcing plate.

[0028] If the step height is greater than the thickness of the reinforcing plate, the outer surface of the leg section extending downwards from the step protrudes beyond the outer surface of the reinforcing plate. This can be advantageous depending on the specific component.

[0029] The reinforcing plate has a length extending along the longitudinal axis of the base body or the longitudinal section. The length of the reinforcing plate preferably extends over at least 30% of the length of the longitudinal section.

[0030] Within the scope of the invention, it is also possible to arrange several reinforcing plates spaced apart from one another, preferably having a total length of at least 30%. This can be the case, for example, in the area of ​​the hinge connections at B-pillars and A-pillars as bending beams.

[0031] The edge section of the reinforcing plate has a length and a width, and the leg of a longitudinal section has a leg width. One aspect of the invention provides that the width of the edge section in or over a partial length of the edge section is at least 50% of the leg width. The reinforcing plate extends over a portion of its length in cross-section into or over the outer legs, specifically at least to half the leg width.

[0032] The edge section has a longitudinal joint. The longitudinal joint forms the outer edge of the edge section. The longitudinal joint is arranged at a distance from the step in the leg, the distance being between 0.5 mm and 12 mm, in particular between 3.0 mm and 8.0 mm.

[0033] Extending from the step is a lower leg section that transitions into an outwardly directed flange. Specifically, the lower leg section transitions into the outer flange via a radius.

[0034] Preferably, the legs have an opening angle of 2° to 10° with respect to a vertical, more preferably the opening angle is 3° to 5°. The opening angle is measured between a vertical and the inside of the leg, both to the upper leg section above the step and to the lower leg section below the step.

[0035] The step in one leg extends, in particular, over the length of the edge section of a reinforcing plate. Therefore, in the case of a bending beam in the form of a B-pillar, the length of the step measured along the z-axis and the length of the edge section are equal.

[0036] A further embodiment of the invention provides that the step is longer than the length of the reinforcing plate. The step thus increases the stiffness of the longitudinal section and the bending beam as a whole and can extend to the connection sections of the bending beam provided at each end, which connect to the longitudinal section.

[0037] The base body and the reinforcing plate have a tensile strength Rm of greater than or equal to (≥) 1,000 MPa. The bending beam, in particular the base body, and the reinforcing plate have a predominantly martensitic and / or bainitic microstructure. The design according to the invention achieves a uniform tensile strength distribution. According to the invention, the base body has a tensile strength Rm in the area of ​​the step, the legs, and the web that varies by a maximum of 150 MPa. This technical effect results from the step provided according to the invention and the resulting avoidance of undercuts.

[0038] A design that improves the overall quality of the automotive bending beam incorporates a layer between the base body and the reinforcing plate. This layer is specifically aluminum-silicon based. It is an alloy layer consisting of the steel of the base body and the reinforcing plate, and a coating material. This coating material is also aluminum-silicon. The layer acts adhesively and improves the bond between the reinforcing plate and the base body. In particular, the layer inhibits corrosion and counteracts crevice and / or contact corrosion.

[0039] It is particularly advantageous for the entire vehicle bending beam, i.e. the base body and the reinforcement plates, to be provided with a coating which is primarily based on aluminium-silicon.

[0040] In a motor vehicle with a bending beam according to the invention, the bending beam preferably forms the B-pillar. The B-pillar extends between a vehicle sill and a roof frame. In an advantageous embodiment, the reinforcing plate is designed such that, when installed in the vehicle, it extends downwards to such an extent that it at least partially or in certain areas overlaps the vehicle sill.

[0041] The invention is described in more detail below with reference to the drawings. These show: Fig. 1 a motor vehicle bending beam according to the invention in the form of a B-pillar in one view; Fig. 2 a section through the representation of the Fig. 1 along line AA; Fig. 3 a section through the representation of the Fig. 1 along line BB; Fig. 4 a section through the representation of the Fig. 1 along line CC; Fig. 5 a section through the representation of the Fig. 1 along line DD; Fig. 6 Another embodiment of a motor vehicle bending beam in the form of a B-pillar in a view; Fig. 7 a section through the representation of the Fig. 6 along line AA; Fig. 8 a section through the representation of the Fig. 6 along line BB; Fig. 9 a section through the representation of the Fig. 6 along line CC; Fig. 10 a section through a motor vehicle bending beam according to the representation of Fig. 6 along line BB with a variant of the step configuration; Fig. 11 another embodiment of a motor vehicle bending beam in the form of a B-pillar; Fig. 12 another embodiment of a motor vehicle bending beam in the form of a B-pillar; Fig. 13 a section through the representation of the Fig. 12 along line AA; Fig. 14 a section through the representation of the Fig. 12 along line BB and Fig. Figure 15 shows a technically schematic side view of a motor vehicle bending beam.

[0042] In the Fig. For parts 1 to 15 that are identical or functionally equivalent, the same reference symbols are used, even if, for the sake of simplicity, repeated descriptions are omitted. The same applies to dimensions and measurements shown.

[0043] In the Fig. 1, Fig. 6, Fig. 11 and Fig. Figure 12 shows a vehicle coordinate system. A vehicle coordinate system is a three-dimensional Cartesian coordinate system used to define the axes within a motor vehicle. The x- and y-axes lie in a horizontal plane (the vehicle plane). The x-axis corresponds to the vehicle's longitudinal axis, the y-axis to its transverse axis, and the z-axis to its vertical axis.

[0044] Terms such as transverse and longitudinal, top and bottom, horizontal and vertical, or longitudinal direction, longitudinal and transverse direction, transverse, as well as edge-side, top-side or bottom-side, refer to the installation position of the respective motor vehicle bending beam in the motor vehicle.

[0045] In the Fig. 1, Fig. 6, Fig. 11 and Fig. Figure 12 shows a vehicle bending beam according to the invention in the form of a B-pillar 1 in a view from the outside of a vehicle. Fig. Figures 2 to 5, 7 to 10, 13 and 14 each show cross-sectional views through the structure shown in the Fig. 1, Fig. 6, Fig. 11 and Fig. 12 depicted section paths.

[0046] The B-pillar 1 comprises a base body 2 made of hardenable or hardened steel and a reinforcing plate 3 made of hardenable or hardened steel joined to the base body 2. The base body 2 and the reinforcing plate 3 are formed together, in particular hot-formed in a forming or pressing tool and press-hardened.

[0047] The base body 2 has a longitudinal section 4 extending in the z-direction (vehicle vertical axis). An upper head section 5 and a lower foot section 6 are attached to this in the plane of the image. The head section 5 serves to connect the B-pillar 1 to a roof frame. The foot section 6 serves to connect the B-pillar 1 to a vehicle sill.

[0048] The base body 2 has a hat- or U-shaped cross-section in its longitudinal section 4, with two lateral legs 7 and a web 8 connecting the legs 7. The reinforcing plate 3 is arranged in the longitudinal section 4. The reinforcing plate 3 is bonded to the base body 2 and is located on the outside of the base body 2. The reinforcing plate 3 also has a hat- or U-shaped cross-section and a back 9 to which a leg-side edge section 10 is attached on both sides. The leg-side edge sections 10 of the reinforcing plate 3 abut each leg 7 of the longitudinal section 4 of the base body 2.

[0049] The back 9 rests against the outer surface of the web 8. The reinforcing plate 3 has a length LV and extends over at least 30% of the length LL of the longitudinal section 4. The head edge 11 and the foot edge 12 of the reinforcing plate 3 are in the Fig. 1, Fig. 6, Fig. 11 and Fig. 12 each shown with a dashed line.

[0050] The edge sections 10 each extend along a step 13 formed in the legs 7. This is shown in particular by the illustrations of the Fig. 3, Fig. 8, Fig. 10 and Fig. 14.

[0051] The Fig. Figure 2 shows a section through the B-pillar 1 according to the representation of Fig. 1. There, it can be seen that the longitudinal section 4 towards the head section 5 has a hat- or U-shaped cross-sectional configuration with the two legs 7 and the web 8 connecting the legs 7. At the end of each leg 7, an outwardly directed flange 15 is connected via a transition 14, which runs in a radius.

[0052] The Fig. Figure 3 illustrates that the reinforcing plate 3 is flush with the outer surface of the step 13 of the base body 2 along the edge section 10. The outer surface of the reinforcing plate 3 and the outer surface of the longitudinal section 4 or the lower leg sections 16 running along the step 13 are without protrusions.

[0053] Each step 13 extends to the lower foot section 6 of the B-pillar 1, which extends to the left and right of the longitudinal section 4 (see Fig. 4).

[0054] The Fig. Figure 5 illustrates that the reinforcing plate 3 extends into the base section 6 of the B-pillar 1 and is designed to extend downwards to such an extent that the reinforcing plate 3 partially overlaps the area of ​​the vehicle sill 20 running behind the base section 6. This measure leads to an improvement in stiffness behavior with regard to both longitudinal and lateral stiffness and has a beneficial effect on crash behavior.

[0055] The Fig. 7 and Fig. Figure 8 shows sections through B-pillar 1 according to the representation of Fig. 6. The reinforcing plate 3 extends in length section 4 with its edge sections 10 along each step 13 in the legs 7. The steps 13 have a length LS which corresponds to the length LR of the edge section 10 of the reinforcing plate 3.

[0056] In the Fig. 7 and Fig. Figure 8 shows the opening angle α. The opening angle α is measured between a vertical line and leg 7.

[0057] The Fig. Figure 8 shows the opening angle α between the upper leg section 17 above the step 13 and the lower leg section 16 below the step 13. This is the same in the illustrated embodiment.

[0058] The opening angle α lies in a range between 2° and 10° and in particular between 3° and 5°.

[0059] The presentation of Fig. Figure 9 shows a section through a sill section 18 extending in the x-axis of the foot section 6. It can be seen that there is no step 13 there.

[0060] The Fig. Figure 10 shows an alternative embodiment of the B-pillar 1 in the central longitudinal section 4. The step 13 is more pronounced. The step 13 has a step height s that is greater than the thickness d of the reinforcing plate 3. Accordingly, the lower leg section 16, or rather its outer surface, is slightly offset outwards from the outer surface of the edge section 10 of the reinforcing plate 3.

[0061] An edge section 10 of the reinforcing plate 3 has a length LR and a width BR. The leg(s) 7 have a leg width SB. The width BR of the edge section 10 is at least 30% of the leg width SB over at least part of its length. In particular, over a middle section TL, the width BR of the edge section 10 is greater than half the leg width SB. The width BR of the edge section 10 can decrease and taper towards the end at either the upper or lower end of a reinforcing plate 3.

[0062] The Fig. Figure 15 shows a simplified side view of a B-pillar 1. Fig. Figure 15 serves to illustrate the configuration of the reinforcing plate 3 and its length LR and width BR. With respect to the leg width SB of a leg 7, the width BR of the edge section 10 is greater than half the leg width SB in a partial length TL of the edge section 10. The width BR of the edge section 10 extends over 75% ± 15% of the leg width SB. The edge section 10 tapers towards the head edge 11 and the foot edge 12 of the reinforcing plate 3.

[0063] The Fig. Figure 13 clarifies that a B-pillar 1, as in the Fig. As shown in Figure 12, the head section 5 can also each have a step 13 in the legs 7. The step 13 extends from the head section 5 over the length section 4 (see Figure 12). Fig. 14) up to the sill-side foot section 6. The section there along the section line CC corresponds to the representation of Fig. 4.

[0064] An edge section 10 has a longitudinal joint 19 at its free end. The longitudinal joint 19 is arranged at a distance a from the adjacent step 13. The distance a is between 0.5 mm and 12 mm. In particular, the distance a is between 5.0 mm and 8.0 mm.

[0065] In all embodiments of the B-pillar 1, the base body 2 and the reinforcing plate 3 have a tensile strength Rm of greater than or equal to ≥ 1,000 MPa and possess a martensitic and / or bainitic microstructure. The strength distribution is uniform across the components. In the area of ​​step 13, as well as the legs 7 and the web 8, the base body 2 has a tensile strength Rm that is uniformly high and varies by a maximum of 150 MPa.

[0066] Not shown in the drawings, but advantageous, is the inclusion of a layer between the base body 2 and the reinforcing plate 3. This layer is an aluminum-silicon alloy layer alloyed with the steel of the base body 2 and / or reinforcing plate 3. Reference symbol: 1 B-pillar 2 basic bodies 3 Reinforcing plates 4 Length section 5 Head section 6 foot section 7 thighs 8 Bridge 9 Back 10 Marginal section 11 Head edge v. 3 12 Foot edge v. 3 13th level 14 Transition 15 flange 16 lower thigh section 17 upper thigh section 18 Sill section 19 Longitudinal impact 20 vehicle sills a distance d Thickness v. 3 step height BR width v. 10 LL Length v. 4 LR length v. 10 LS length v. 13 LV length v. 3 Rm tensile strength SB thigh width TL partial length v. 10 α Opening angle

Claims

[1] A motor vehicle bending beam with a tensile strength (Rm) of greater than or equal to 1,000 MPa, comprising a base body (2) and a reinforcing plate (3) joined to the base body (2), wherein the base body (2) has a longitudinal section (4) having two legs (7) and a web (8) connecting the legs (7), and the reinforcing plate (3) is arranged in the longitudinal section (4), wherein the reinforcing plate (3) abuts a leg (7) with at least one leg-side edge section (10), and the edge section (10) extends along a step (13) formed in the leg (7), characterized by, that the base body (2) and the reinforcing plate (3) are made of hardenable steel and are jointly hot-formed and press-hardened, and that the base body (2) and the reinforcing plate (3) have a tensile strength (Rm) of greater than or equal to 1,000 MPa, wherein the base body (2) has a tensile strength (Rm) in the area of ​​the step (13), the legs (7) and the web (8) which varies by no more than 150 MPa. [2] Motor vehicle bending beam according to claim 1, characterized by , that the reinforcing plate (3) at the edge section (10) along the step (13) is flush with the outer surface of the step (13) of the base body (2). [3] Motor vehicle bending beam according to claim 1, characterized by , that the step (13) has a step height (s) at least in the area of ​​the reinforcing plate (3) which is greater than or equal to the thickness (d) of the reinforcing plate (3). [4] Motor vehicle bending beam according to one of claims 1 to 3, characterized bythat the reinforcing plate (3) extends over at least 30% of the length (LL) of the longitudinal section (4). [5] Motor vehicle bending beam according to one of claims 1 to 4, characterized by , that the edge section (10) of the reinforcing plate (3) has a length (LR) and a width (BR) and the leg (7) has a leg width (SB), wherein the width (BR) of the edge section (10) in a partial length (TL) of the edge section (10) is at least 50% of the leg width (SB). [6] Motor vehicle bending beam according to any one of claims 1 to 5, characterized by , that the edge section (10) has a longitudinal joint (19) and the longitudinal joint (19) is arranged at a distance (a) from the step (13), wherein the distance (a) is dimensioned between 0.5 mm and 12 mm, in particular between 3.0 mm and 8.0 mm. [7] Motor vehicle bending beam according to any one of claims 1 to 6, characterized by, that starting from the step (13) a lower leg section (16) extends, which transitions into an outwardly directed flange (15). [8] Motor vehicle bending beam according to any one of claims 1 to 7, characterized by , that the step (13) is longer than the length (LV) of the reinforcing plate (3). [9] Motor vehicle bending beam according to any one of claims 1 to 8, characterized by , that a layer is provided between the base body (2) and the reinforcing plate (3), in particular an aluminium-silicon-based layer. [10] Motor vehicle with a motor vehicle bending beam according to one of claims 1 to 9, wherein the bending beam forms a B-pillar (1) and extends between a vehicle sill and a roof frame. [11] Motor vehicle according to claim 10, characterized by , that the reinforcement plate (3) overlaps the vehicle sill in some areas.

Images