Door ring for the body of a motor vehicle

Abstract

The invention relates to a door ring (1) for a motor vehicle body comprising individual components coupled in the form of an A-pillar (2), a B-pillar (4), a roof frame part (3), and a sill part (5), wherein at least in one area a tensile strength Rm greater than 1300 MPa is formed and in another area a tensile strength Rm less than 1000 MPa is formed, wherein the door ring (1) has a corrosion protection layer, characterized in that the components are laser-welded with an overlap, in particular a lap joint, and in that the corrosion protection layer is formed between the overlapping layers (9, 11).

Description

[0001] The present invention relates to a door ring for a motor vehicle body according to the features in the preamble of claim 1.

[0002] It is known from current technology to manufacture motor vehicle bodies as so-called unibody constructions. Such motor vehicles are powered by internal combustion engines, but increasingly also by electric motors in recent times.

[0003] A self-supporting vehicle body has individual body components, such as the A-pillar, B-pillar, C-pillar, a sill, various cross and longitudinal members, a window frame, a roof frame, a roof, as well as various floor panels and other attachments.

[0004] For this purpose, individual components are processed using forming techniques and then joined together, in particular welded. This creates a self-supporting vehicle body.

[0005] It is known from the prior art to prefabricate components or component groups. In particular, a so-called door ring, also known as a door ring in English, is known for mounting a motor vehicle door.

[0006] Such a door ring has an A-pillar at the front and a B-pillar at the rear or middle, between the driver's door and behind it. At the roof, the A-pillar merges into at least part of the roof frame. A sill is located at the bottom. This creates a continuous ring through which a passenger can enter the vehicle body. This ring is later closed by a vehicle door.

[0007] In cross-section, these can be shell components that are coupled with additional strike plates or similar elements. However, the door ring is initially a raw component and, according to this invention, can be designed as a single shell. As mentioned, additional strike plates can be added later during body construction.

[0008] For example, US patent 2021 / 221439 A1 discloses the production of a tailor welded blank in which the pre-coating is removed from the areas to be welded on pre-coated material.

[0009] Furthermore, a door ring of a motor vehicle is known from CN 115 056 856 A.

[0010] Furthermore, a method for manufacturing a hot-formed and press-hardened component is known from DE 10 2020 212 136 A1.

[0011] The object of the present invention is to provide a door ring which offers specifically improved strength properties, improved corrosion protection properties, and at the same time more favorable manufacturability.

[0012] The aforementioned problem is solved with a door ring according to the features in claim 1.

[0013] Advantageous embodiments of the present invention are described in the dependent claims.

[0014] The door ring of a motor vehicle body comprises several interconnected components, including an A-pillar, a B-pillar, a roof frame section, and a sill section. The door ring can also be designed as a double door ring. In the longitudinal direction of the vehicle, this also incorporates the door behind the driver's door and the passenger's door, respectively. Therefore, the door ring would then also include another longitudinally extending section of the roof frame, a C-pillar, a rear sill section, and potentially parts of a wheel arch or wheel housing located behind it.

[0015] As mentioned earlier, this door ring is initially shown in cross-section as a single-layer component. Additional components, strike plates, or similar items can be added.

[0016] The door ring is characterized, at least in sections, by having a strength, particularly a tensile strength Rm, greater than 1300 MPa, preferably greater than 1500 MPa, and particularly greater than 1800 MPa, in at least individual components. However, the tensile strength Rm should not exceed 2200 MPa. This is made possible by using a hardened steel for at least one of the interconnected components of the door ring. The steel can either be an ultra-high-strength steel produced by a cold forming process, or, in particular, a hardenable steel, such as a manganese-boron steel, which is formed by hot forming and press hardening. The component then exhibits, at least in certain areas, the tensile strengths described above in hard or solid regions. Each region is formed, in particular, by a component. Thus, an A-pillar (or...) can be considered a component.The components include the roof frame, a B-pillar, and a sill. These components are made from different grades of steel. For example, some components may be made from hardenable manganese-boron steels, while others may be made from conventional steel grades. As described below, the components are coated with a corrosion protection layer and laser-welded together.

[0017] Where complete hardening for maximum tensile strength is desired, namely the upper area of ​​the B-pillar (including the roof frame stub) and the upper areas of the A-pillar and roof frame, a press-hardenable steel alloy (steel A to D) is used, while areas or components acting primarily as deformation zones in a side impact, such as the sill, the lower foot area of ​​the B-pillar, and the sill stub or lower part of the A-pillar, consist of non-hardenable or barely hardenable steel (steel E or F) with a tensile strength below 1000 MPa (e.g., 500 to 800 MPa). The chemical analyses of the individual steel alloys (steel A to F) preferably used according to the invention, as shown in the following table, contain values ​​in mass percent and show iron as the remainder and impurities unavoidable during melting. For preferably present reinforcement patches or...Reinforcing plates on the A-pillar and B-pillar can also be made of one of the steels A to D, with steel C or D being particularly preferred, since a tensile strength above 1900 MPa can be achieved after press hardening, while steels A and B have a tensile strength just above 1400 MPa after press hardening.

[0018] The door ring then has further areas or coupled components that have a tensile strength Rm of less than 1000 MPa, in particular less than 850 MPa. However, the tensile strength Rm should be at least 350 MPa, and preferably at least 500 MPa, even in these relatively softer areas.

[0019] Furthermore, the door ring and / or steel components have a corrosion protection layer, which preferably has the same coating, including the same layer thickness and specific layer weight, on all components coupled to the door ring. Alternatively, the sill and B-pillar base can have a higher-quality, thicker, and / or heavier corrosion protection layer than the A-pillar, roof frame, or upper B-pillar.

[0020] According to the invention, at least two of the individual components are laser-welded to one another with an overlap joint, at least in certain areas. According to the invention, the corrosion protection layer is also formed between the overlapping layers. The overlap joint allows for simple and efficient joining of the components, compensating for any component tolerances. The overlap also compensates for differences in length.

[0021] According to the invention, at least two components are then welded together in at least one area by means of overlapping and laser welding.

[0022] Different strength levels can be set. Alternatively or additionally, different wall thicknesses can be used in the areas of varying strength to create different stiffness properties of the door ring.

[0023] On hot-formed components, the corrosion protection layer is primarily based on an aluminum-silicon-iron alloy. Such a corrosion protection layer is particularly suitable for hot-formed and press-hardened components. These components are therefore pre-coated. The AlSi coating can have a layer thickness of 10 µm to 45 µm, but in particular, a relatively low layer weight of 20 g / m² to 90 g / m² per sheet side and / or a layer thickness of 10 µm to 25 µm is applied to reduce the negative influence of the aluminum and intermetallic phases on the weld joint. If the component is heated above the austenitizing temperature, i.e., above the Ac3 temperature, the pre-coating undergoes alloying. In the case of cold-formed components, such as UHSS components, a zinc-based corrosion protection layer can be used.

[0024] The laser welding according to the invention is carried out in particular as remote laser welding. For this purpose, wire-free weld seams are preferably formed at least along one line or joint area. Since the laser weld seams according to the invention are only created after the hot forming and press hardening of at least some of the components or joining partners, they are recognizable on the finished door ring as a heat-affected zone caused by welding by measuring the hardness profile transverse to joint areas and are distinguishable from those weld joints that are already created on the level of undeformed sheet metal blanks and only subsequently undergo a hot forming process. In particular, the door ring according to the invention has a characteristic discontinuous hardness profile in the joint area with a hardness peak and hardness depressions descending on both sides from it, which result from the heat input of the welding laser beam as a kind of small-area local tempering. The hardness drop, at least in the component or joining partner, isHowever, the area of ​​hardenable steel is particularly less than 30% or less than 25% compared to press-hardened areas outside the heat-affected zone.

[0025] Especially in radii or curved joint areas, a wire-containing weld can be used for better gap or tolerance compensation. "Wire-containing" refers specifically to a welding filler material.

[0026] Alternatively or in addition to a wire-containing weld, an oscillating or rotating movement of the laser beam can be performed with increased melting power controlled by the gap.

[0027] The overlap area between one component and the next is less than 25 mm, particularly preferably less than 20 mm, particularly less than 15 mm, and most preferably less than 10 mm. However, the overlap area should be at least 2 mm, particularly preferably 5 mm.

[0028] Herein lies a further advantage of the invention. When two layers overlap, a weld is performed starting from the surface of one layer, which then completely penetrates the upper layer and enters the layer below. In such a case, a weld root is formed that is oriented essentially perpendicular to the surface. This weld root preferably penetrates less than 90%, and particularly less than 80%, of the second layer. This has the advantage, firstly, due to manufacturing considerations, that good welding of the two layers takes place in this area. A further advantage is that the corrosion protection layer on the underside of the second layer is not attacked by a weld seam that completely penetrates the second layer. Thus, good corrosion protection is provided on the reverse side of the weld seam. In the area where the weld seam penetrates, or...The weld root from the first layer to the second layer and the corrosion protection layer located between the layers also provides particularly good corrosion protection.

[0029] According to the invention, it has further been shown that, depending on the corrosion protection layer used, the top surface of the weld seam melts or mixes with this corrosion protection layer and, likewise, after completion of the laser welding process, the top surface of the weld seam is also corrosion-protected.

[0030] As an alternative to the previously described weld seam, which is essentially perpendicular to the surface, an inclined weld root could be used. Starting from an overlapping layer, the end face and first layer extend diagonally through the cross-section into the second layer. This occurs at an angle between 30° and 45°, and particularly between 20° and 50°.

[0031] One advantage of this method is that, since the end face is sometimes free of corrosion protection coating material, less corrosion protection material is carried into the weld itself. This improves the weld quality. After welding, the top surface of the weld can then be coated with a final corrosion protection layer. Furthermore, welding consumables, especially wire, can be used with this type of weld design, allowing for the bridging of larger weld gaps without requiring additional melting of the upper layer facing the laser beam during welding, and / or the use of oscillating laser beams or adaptive power levels.

[0032] Another advantage of the laser welding process is that the weld seam does not have to run parallel or transversely to the longitudinal axis of the two overlapping areas. In particular, it can follow a wave-like, zigzag, or sawtooth pattern. This improves heat transfer into the component and the strength of the weld joint, as a relatively larger area is joined, further enhancing the joint's strength. Stresses and / or heat influences are better compensated for within the material by the wave-like weld seam. In the event of a crash, local stress peaks and loads perpendicular to the weld seam are reduced or transformed into a more oblique load.

[0033] In accordance with the invention, a reinforcing patch can also be incorporated. This results in a double layer, for example, in the area of ​​the A-pillar or the B-pillar, such as in the area of ​​door attachment points or crash-prone areas. A reinforcing patch can also be incorporated, for example, in the area of ​​the rocker panel. The reinforcing patch is preferably spot-welded. The reinforcing patch can then be hot-formed and press-hardened, for example. Alternatively, it is also possible, for example, to incorporate the reinforcing patch later in a cold-formed component, with the reinforcing patch itself being formed separately.

[0034] The reinforcement patch can also span two adjacent components. Thus, the reinforcement patch can provide additional reinforcement in the joint between two components.

[0035] According to the invention, it is also possible to weld through a triple layer. In this case, not only are two adjacent components lying on top of each other, but three layers are formed in cross-section. Here too, preferably less than 95%, particularly less than 90%, and most preferably less than 80% of the wall thickness of the bottom layer is welded through. This again offers the advantage that the corrosion protection layer on the underside of the bottom layer is not disturbed.

[0036] Further advantages, features, properties, and aspects of the present invention are the subject of the following description. Preferred embodiments are illustrated in schematic figures. These serve to facilitate understanding of the invention. They show: Figure 1: a door ring; Figure 2: a rear view of the one in Figure 1Figure 3 shows a detailed view of the B-pillar, Figure 4 another detailed view of the B-pillar, Figure 5 another embodiment of a door ring according to the invention, Figure 6 a connection area in cross-sectional view, Figure 7 another embodiment of the weld seam produced by laser welding, Figure 8 another embodiment of the present invention, Figure 9 another embodiment of the weld seam produced by laser welding, Figure 10 a weld seam path in its longitudinal direction, Figure 11 alternative to Figure 10 .

[0037] The same reference symbols are used in the figures for identical or similar components, even if a repeated description and representation is omitted for the sake of simplicity.

[0038] Figure 1Figure 1 shows a door ring 1. The door ring 1 has an A-pillar 2, part of a roof frame 3, a B-pillar 4, and part of a sill 5. This door ring 1 can initially be designed as a single-shell cross-section. In the area of ​​the A-pillar 2, in the area of ​​the B-pillar 4, in the area of ​​the roof frame 3, and also in the area of ​​the sill 5, strike plates or closing half-shells, or even an inner door ring made in one piece from a custom-welded sheet metal blank (abbreviated: TWB), can be applied, so that a high profile results in at least partially, and in particular completely, in the cross-section. The subject of this invention is primarily the single-shell configuration as shown. Figure 1The B-pillar base can, as shown here, be T-shaped, resulting in a sill stub 4.1 or 4.2, respectively. The same applies to the A-pillar 2, where a sill stub 2.1 can also result. The roof frame 3 can project rearward in the longitudinal direction X of the vehicle. Various connection areas 6 or overlap areas between the components are formed here. For example, in each of the connection areas according to reference numeral 6, the individual components are either subdivided and welded together by means of an overlap. Otherwise, two adjacent components are welded together. For the purposes of this entire disclosure, the upper area of ​​the A-pillar 2 and the roof frame 3 can be considered a single component. Thus, the A-pillar 2 extends to the B-pillar 4. However, the A-pillar 2 and roof frame 3 can also be considered as a single component, as shown in Figure 1The image shows two components that are welded together.

[0039] Figure 2 shows a rear view of the in Figure 1 The variant shown. Here, a reinforcement patch 7 is attached from the rear inside in the area of ​​the A-pillar 2. This reinforcement patch 7 is welded to the A-pillar 2 over a large portion. Furthermore, a reinforcement patch 8 is attached to the rear, i.e., in the B-pillar 4.

[0040] While the reinforcement patch 7 of the A-pillar was press-formed and, in particular, press-hardened together with the A-pillar itself in a single forming step, the reinforcement patch 8 of the B-pillar may also have been added after forming. This is especially true if, as shown, it is designed and positioned to extend into the T-shaped base of the B-pillar, so that it protrudes beyond the weld seam in the connection area 6.

[0041] Figures 3 and 4Each image shows a detailed view of the B-pillar 4. An overlap is shown here, which will be discussed further below. In particular, in the Figure 4 Further spot welds are shown. These can be used for coupling with the reinforcement patch 8.

[0042] Figure 5Figure 1 shows a further embodiment of a door ring 1 according to the invention. Here, the respective transition areas 6 and connection areas between two components are shown. The vehicle sill 5 extends over a large portion in the vehicle's X-direction and is connected to an A-pillar 2 at the front. This results in a small A-pillar stub 2.1, the B-pillar 4 with its lower base is directly formed by the sill 5 and is then coupled above the B-pillar base. The B-pillar 4 includes an upper T-piece in the area of ​​the roof frame 3. This can also be referred to as a roof frame stub at the B-pillar 4. This is then coupled to the A-pillar 2 in a connection area 6.

[0043] Figure 6Figure 1 shows a connection area 6 in cross-sectional view. An upper layer 9, or first layer of a component, overlaps in an overlap area 10. A lower layer 11, or second layer of a second component, overlaps in this area. The overlap area 10 has a transverse extent of less than 25 mm. A weld seam 15, or weld root, is applied from a top surface 12 of the upper layer 9. It extends to a depth 13. The first, or upper layer 9, penetrates completely into the second layer. However, in the lower layer 11, the weld seam preferably penetrates less than 95%, and particularly less than 90%. This offers the advantage that a surface coating on the underside 14 of the lower layer 11 is not affected by the weld seam 15 burning through, and that aluminum from the coating of the underside 14 does not mix with the weld pool during welding.The corrosion protection layer on the underside of the layer remains completely intact. In particular, this option, whereby the weld seam 15 or weld root is formed essentially perpendicular to the surface of the layers, offers the possibility not only of forming a linear weld seam 15, but the weld seam 15 can, for example, be wavy, zigzag, or even follow the principle of a sawtooth profile in its longitudinal direction.

[0044] The respective corrosion protection layer is not shown in detail here, but is also formed in the overlap area 10 between layers 11, 17, so that the overlap area 10 is also corrosion protected.

[0045] Figure 7Figure 1 shows a further embodiment of the weld 15 produced according to the invention by laser welding. Here, the weld 15 is applied at an angle, specifically at an angle α preferably in the range of 30° to 45° to the respective surfaces of layers 11 and 17 relative to each other. This offers the advantage that the weld 15 is applied from an end edge 16 of the upper layer. The end edge 16 can also be referred to as the cutting edge. Any corrosion protection layer present at this end edge 16 is initially only partially formed or not formed at all. No corrosion protection layer is introduced into the weld 15 itself, which further improves the quality of the weld 15 and thus the strength to be achieved.

[0046] Figure 8 shows a further embodiment of the present invention. Here, unlike in Figures 6 and 7A double layer is shown, or a triple layer. A further layer 17, for example a reinforcing patch or similar, is also arranged. The lowest layer 11, shown on the plane of the image, is penetrated by the weld 15 to a depth of less than 95%, preferably less than 90%. A surface coating on the underside is therefore not damaged by the weld 15.

[0047] Analogous arguments to Figure 7 also applies to Figure 9 . Here, the weld seam 15 is applied at an angle to the surface and joins the three layers together.

[0048] Figure 10 Figure 1 shows an example of a weld seam profile in its longitudinal direction. This profile is formed according to the principle of a wave shape. In this case, a B-pillar 4 or a B-pillar base is connected to a sill 5. The weld seam 15 is shaped according to the functional principle in cross-section as shown. Figure 6It is introduced and can have a wavy profile. This increases the length and thus also the effective cross-sectional area of ​​the weld, which advantageously also results in a reduced local stress concentration under crash-related or mechanical stresses.

[0049] Figure 11 Figure 1 shows an alternative design variant. Here, a front edge 16 of the B-pillar base is shown on the underside 14. This edge itself exhibits a wavy profile. The weld 15 is designed according to the functional principle in cross-section as shown. Figure 7 .

[0050] The steel grades used below can be considered examples and are suitable for all variants of this invention. In particular, different steel grades can be combined in a tailored welded blank. Corresponding strength ranges for hard or soft areas, or solid or ductile areas, can be found in the table. All alloying elements are given in wt.%, to which residual iron and melting-related impurities are added for each hardenable steel alloy. Reference symbol:

[0051] 1 - Door ring 2 - A-pillar 2.1 - Sill stub 3 - Roof frame 4 - B-pillar 4.1 - Sill stub 4.2 - Sill stub 5 - Sill 6 - Connection area 7 - Reinforcement patch to 2 8 - Reinforcement patch to 4 9 - Upper layer 10 - Overlap area 11 - Lower layer 12 - Top 13 - Depth 14 - Bottom to 11 15 - Weld seam 16 - Face edge 17 - Further layer X -longitudinal direction of motor vehicle α -angle

Claims

1. Door ring (1) for a motor vehicle body, comprising individual components coupled to one another in the form of an A-pillar (2), a B-pillar (4), a roof frame part (3), and a sill part (5), wherein a tensile strength Rm greater than 1300 MPa is formed in at least one region and a tensile strength Rm less than 1000 MPa is formed in another region, wherein the door ring (1) has a corrosion protection layer, wherein the components in the regions comprise at least two different steel grades and are laser-welded with an overlap, characterized in that the corrosion protection layer is formed between the overlapping layers (9, 11) and that the overlap is less than 25 mm.

2. Door ring (1) according to claim 1, characterized in that at least one of the coupled components of the door ring (1) is manufactured as a hot-formed and press-hardened component, in particular in a single press stroke.

3. Door ring (1) according to claim 1 or 2, characterized in that a high-strength region has a tensile strength Rm greater than or equal to 1800 MPa.

4. Door ring (1) according to one of the preceding claims, characterized in that soft regions are formed which have a tensile strength Rm of less than 1000 MPa, preferably less than 850 MPa, and / or that the soft regions have a smaller wall thickness.

5. Door ring (1) according to one of the preceding claims, characterized in that the corrosion protection layer is formed on an AlSiFe basis or that the corrosion protection layer is formed on a Zn basis.

6. Door ring (1) according to one of the preceding claims, characterized in that the individual components are laser-welded to form the door ring.

7. Door ring (1) according to one of the preceding claims, characterized in that the weld seam (15) of the laser welding formed between two coupled components consists exclusively of the chemical elements of the steel grades of the two components as well as of the chemical elements of the corrosion protection layer.

8. Door ring (1) according to one of the preceding claims, characterized in that the overlap is less than 20 mm, particularly preferably less than 15 mm, and most preferably less than 10 mm.

9. Door ring (1) according to one of the preceding claims, characterized in that, in the region of the overlap, an inclined weld root is introduced between the two overlapping parts.

10. Door ring (1) according to one of the preceding claims, characterized in that, in the region of the overlap, the weld seam is introduced from both component edges, or that a weld root that is straight in cross-section is introduced, which extends perpendicular to the overlap.

11. Door ring (1) according to one of the preceding claims, characterized in that the weld root penetrates less than 90% of the second component in cross-section.

12. Door ring (1) according to one of the preceding claims, characterized in that the weld seam between two coupled components extends over at least 60%, preferably at least 70%, in particular 80% of the total cross-sectional length / developed length.

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