EP2959985B1 - Profiled beam with increased flexural strength made of cold strip and method for producing same - Google Patents

Description

The invention relates to a method for producing profiled carrier with an increased bending strength according to the preamble of claim 1.

Such a method is eg in the US-A-3850019 disclosed.

In vehicle long moldings are used, which are made of sheet metal, which is spatially deformed to increase the bending strength, thereby increasing the area moment of inertia of the component with the same material use. Thus, it is known, for example, to design the B and C pillars in cars which in the event of a side impact absorb a large part of the energy transmitted by the vehicle as a profiled beam bent over the length with a U-shaped profile cross-section which consists of flat metal sheet be formed with a homogeneous initial thickness. Although the flexural strength of the structural beams is significantly increased by the spatial deformation of the material compared to flat material, it is desirable in view of the increasing tendency in recent years to reduce the weight of motor vehicles and the ever increasing safety requirements, the bending strength of such profile beam at a given weight of each component without increasing the cost of manufacturing the components, for example, by the use of higher quality materials.

Accordingly, it is an object of the present invention to provide a method for producing a profile carrier made of sheet metal, in particular a side impact protection in a car, which has an increased component strength and a predetermined material quality increased flexural strength.

This object is achieved by a method having the features of claim 1.

Further features of the invention are contained in the subclaims.

The profile carrier produced by the method according to the invention is preferably made of cold-rolled steel sheet, i. so-called cold strip, which has a substantially homogeneous material thickness at the beginning of the manufacturing process. Although the profile carrier is preferably used as a side impact protection in a motor vehicle, it is basically also suitable for use in other applications, for example as a carrier in a supporting structure of a building or structure, such as a skyscraper, a bridge or dome.

The profile carrier according to the invention in this case has in the simplest embodiment, a substantially U-shaped cross-sectional shape with a first force application surface on which at least a first and a second extending at an angle to the force application surface web are arranged, which extend over the length of the profile carrier away. As far as is spoken in the present application of a force application surface, this is the surface of the carrier to be designated, at which an external force acts on the carrier. This is in the case of the above-mentioned simplest embodiment of the U-shaped section beam, the back of the U-profile which is e.g. in the case of a side impact protection in a car first comes in contact with the colliding vehicle. The profile carrier according to the invention is in this case clamped in the case of a side impact protection at its ends, which can be done for example by welding to the upper and lower door spar.

According to the method of the invention, the profile carrier in the basic embodiment described above is prepared by first a steel strip is fed with a substantially constant initial thickness of a pair of rollers, which alternately adjacent areas having different diameters, such that the steel strip after the rolling to different thicknesses one of the first force application surface associated region having an increased material thickness and a first and second on both sides of this area subsequent region having a reduced material thickness, which are associated with the first and second web. After that, then the rolled to different thicknesses steel strip spatially deformed in particular by forming rollers in such a way that the areas with reduced material thickness with formation of the webs, which correspond to the two legs of the U-shaped cross section in the basic embodiment of the profile carrier, preferably parallel to each other and preferably at right angles to the area extend enlarged material thickness, which corresponds in this case the back of the U-shaped profile carrier. Instead of forming rollers, however, it is also possible that cut to different thicknesses rolled metal strip after rolling in blanks and then transform it by a press in the spatial shape of the profile carrier.

The invention provides the advantage that the flexural strength of the tread carrier due to the additional material in the region of increased material thickness, i. in the region of the back of the U-shaped support, compared to a support which is made of the same material with a constant material thickness, disproportionately increased. This additional gain in flexural strength is obtained not only by virtue of the fact that the thickened region as such has a larger area moment of inertia overall, but by virtue of the fact that this region, due to its increased thickness, can absorb higher thrust forces as a whole, which acts on the force application surface upon application of a force in the normal direction act within the material of the force application surface in the longitudinal direction of the carrier, without causing distortions of the material. In addition, cold rolling of the material occurs in the areas of reduced material thickness due to the rolling, which in turn leads to these areas, i. the legs of the U-shaped profile carrier, in the case of the basic embodiment, have a higher strength than is the case with a conventional carrier of equal weight, which has been manufactured by forming from a material with a constant material thickness.

Another advantage of the profile carrier produced by the process according to the invention is that the material due to the opposite of the other two areas not or less strongly work hardened thickened area can be significantly better shape, as the material in the corner areas during the forming process Simply put, it is pulled out of the softer and more ductile material of the thickened back area. In contrast, the material flows during the forming process from the adjacent work hardened areas, which form the legs / webs of the finished shaped support, almost not, so that they do not constrict or are otherwise adversely deformed.

According to a further embodiment of the invention, the rolling of the steel strip to different thicknesses further comprises the production of a second region of increased material thickness adjoining the second region of reduced material thickness and of a second force application surface, and a third region of reduced material thickness adjoining the second region. Correspondingly, in this embodiment, the forming includes bending the second region of increased material thickness at a preferably right angle to the adjacent second region of reduced material thickness and bending the third region of reduced material thickness at a preferably also right angle to the second region of increased thickness , so that a profile carrier is formed with a substantially S-like cross-section. The latter accordingly has two force application surfaces which are offset and arranged parallel to each other and are interconnected by a central web formed by the second region of reduced material thickness.

According to a further idea underlying the invention, the rolling of the steel strip to different thicknesses further comprises the production of a third region with an increased material thickness which adjoins the third region of reduced material thickness and a third force application surface and a fourth region adjoins this with a reduced thickness material thickness. After the rolling of the steel strip in the manner described above, this is by a forming device, such as forming rollers, a folding device or a press reshaped so that the third area with increased material thickness at right angles to the adjacent third area with reduced material thickness and the fourth area with Reduced material thickness at right angles to the third region with increased thickness run, so that a profile carrier is formed with a cross section which has the shape of two spaced-apart inverted U's, whose adjacent legs are interconnected by a horizontal bar.

The profile carrier according to the invention produced in this way has compared to the previously described embodiments, a further increased flexural strength, the two horizontally extending first and third force application surfaces when used as a side impact protection in a motor vehicle preferably to the outside of the vehicle facing to the colliding vehicle first in Get in touch. This embodiment of the profile carrier according to the invention has the advantage that the forces acting in an impact forces on an overall enlarged surface attack on the carrier, which in conjunction with the two additional inner webs of thin-walled kaltverfestigtem material, the risk of local buckling of the profile carrier is further reduced.

In the preferred embodiment of the invention, the transitions between the sections of increased thickness and the sections of reduced thickness after the rolling of the steel strip and prior to the forming thereof are designed sharp-edged. By this - in the mathematical sense - unsteady transitions profiled substrates are obtained after forming the rolled steel strip, which have consistently flat back and side areas and well-defined edges.

According to an alternative embodiment of the invention, the transitions between the sections of increased thickness and the sections of reduced thickness after the rolling of the steel strip have a continuous course, ie an edgeless transition. This results after forming a profile carrier in which the transitions between the back and the lateral webs are fluid, ie the longitudinal edges have a rounded cross-section. A particular advantage of this embodiment is that the material can flow out of the intermediate areas or transition areas during the forming process, which causes the Facilitated transformation process and reduces the risk of cracking in the area of the rounded longitudinal edges.

In order to further increase the differences in strength between the rolled areas of reduced thickness and the areas of increased thickness and thereby further improve the strength of the finished beam as a whole, the rolling of the steel strip to different thicknesses in the preferred embodiment of the invention by a roller with an open caliber , As a result, the material thickness is not changed in the region or regions with increased thickness during the rolling, so that these areas have a significantly higher ductility or formability compared to the adjacent rolled, work-hardened areas.

In contrast, the adjacent areas of reduced thickness, which form the webs in the end product, due to the work hardening on a further increased strength at a reduced weight, which has an overall positive effect on the overall strength of the carrier. In addition, the forming process is facilitated by the fact that the ductility of the thickened area can be adjusted with high accuracy by an appropriate selection of the starting material, since the use of an open caliber no strain hardening occurs in this area and the material in this area therefore his maintains original characteristics. This results in the further advantage that the material is drawn during the forming process when bending the lateral webs against the back almost exclusively from the areas of increased thickness, whereas almost no material flows from the work hardened areas of reduced thickness. Accordingly, no necking processes of the material occur in the area of the webs during the forming process, which further improves the overall strength of the profile carrier according to the invention.

According to another aspect of the invention, forming the rolled steel strip comprises drawing a collar and / or ironing the material in at least one of the regions of increased material thickness. Due to the fact that the material in the areas with enlarged Material thickness according to the invention a significantly greater ductility than in the adjacent cold-strengthened areas, and also more material is available due to the greater thickness, which can flow when pulling out a collar, there is the advantage that cut into the collar thus produced, for example, thread can be about which can be screwed by means of suitable screws other components directly to the outside of the profile carrier according to the invention, without the need for additional nuts or the like must be welded to the workpiece, as is required in conventionally manufactured profile carriers. Similarly, projections or beads can be introduced by stretching the material in the areas of increased thickness, which can also serve for the direct attachment of other components, or for the positive connection of a profile carrier produced by the process according to the invention with other components.

Although cold strip is used as the material in the preferred embodiment of the invention, hot-rolled strip may alternatively be used as the starting material.

Furthermore, to simplify the logistics when using the method according to the invention, it may be advantageous if the supplied steel strip, whether it is cold strip or hot strip, is unwound from a coil, fed to a previously described rolling device and subsequently the steel strip rolled off to different thicknesses rolled up into a coil. The coiled coils can then be transported directly to the forming operations and unwound there again and by appropriate forming devices, such as. continuously and successively transferred to the webs and spine forming rollers in the final shape of the Pofilträger and then cut to length by a suitable cutter to the desired length.

The invention will be described below with reference to the drawings with reference to two preferred embodiments.

Fig. 1a

eine schematische Darstellung eines zwischen einem Walzenpaar angeordneten Stahlbandes mit konstanter Dicke zur Erzeugung eines U-förmigen erfindungsgemäßen Profilträgers vor dem Abwalzen,

Fig. 1b

das Stahlband von Fig. 1a während des Abwalzens,

Fig. 1c

das fertig abgewalzte Stahlband mit einem zentralen Bereich erhöhter Dicke und zwei angrenzenden kaltverfestigten Bereichen verringerter Dicke,

Fig. 1d

das Stahlband von Fig. 1c beim Formen der senkrechten Stege/Schenkel

Fig. 1e

den fertigen Profilträger gemäß der Grund-Ausführungsform,

Fig. 2a

ein Walzenpaar zur Erzeugung eines doppelt U-förmigen Profilträgers zur Verwendung als Seitenaufprallschutz in einem Kraftfahrzeug mit einem dazwischen angeordneten Stahlband vor dem Abwalzen,

Fig. 2b

das Walzenpaar von Fig. 2a während des Abwalzens,

Fig. 2c

das auf unterschiedliche Dicken abgewalzte Stahlband von Fig. 2a und 2b,

Fig. 3a-d

eine weitere Ausführungsform eines erfindungsgemäßen Profilträgers und dessen Herstellung.

In the drawings show:

Fig. 1a

1 is a schematic representation of a steel strip of constant thickness arranged between a pair of rollers for producing a U-shaped profile carrier according to the invention before being rolled off;

Fig. 1b

the steel band of Fig. 1a during rolling,

Fig. 1c

the finished rolled steel strip having a central area of increased thickness and two adjacent work hardened areas of reduced thickness,

Fig. 1d

the steel band of Fig. 1c when forming the vertical webs / thighs

Fig. 1e

the finished profile carrier according to the basic embodiment,

Fig. 2a

a roller pair for producing a double U-shaped profile carrier for use as side impact protection in a motor vehicle with an interposed steel strip before the rolling,

Fig. 2b

the pair of rolls of Fig. 2a during rolling,

Fig. 2c

the steel strip rolled off to different thicknesses from Fig. 2a and 2b .

Fig. 3a-d

a further embodiment of a profile carrier according to the invention and its production.

As in Fig. 1e is shown, comprises a profile carrier produced by the process according to the invention 1 with a U-shaped cross-section a first, as a back designated force application surface 40a, from which two legs, also referred to as webs 60a and 60b extend at right angles and parallel to each other. The first force application surface 40a is a surface into which a force indicated by the arrow F is introduced, such as the impact forces that are exerted on the carrier 1 in the event of a collision by a foreign vehicle, if this as impact protection in the door or Roof area of a motor vehicle not shown closer is used.

To produce the profiled carrier 1 shown in FIG. 1, a steel strip 2 having a substantially constant initial thickness is first fed to a pair of rollers 3a, 3b, of which the lower roller 3b has a constant diameter and the upper roller 3 has two outer sections 5v and an intermediate one Section 5r has a reduced diameter. Through the in Fig. 1b indicated rolling of the steel strip 2 is formed in this in the section 5r one of the first force application surface 40a associated region 4a with increased material thickness, in which the starting material was not or only slightly rolled off. On the other hand, in the two adjoining outer sections 5v the material is severely rolled off, for example up to 20% of the original thickness, whereby a region 6a, 6b of reduced material thickness arises in which the material is work-hardened by the rolling process. Due to this strain hardening, the material in these two regions 6a, 6b with a reduced material thickness has a considerably higher strength than in the region 4a.

The rolled to its final thickness steel strip 2 ( Fig. 1c ) is subsequently removed from the rollers 3a, 3b and fed to a forming device, which in Fig. 1d is symbolized by three forming rollers 7a, 7b and 7c. In this, the first and the second region of reduced material thickness 6a, 6b, which are assigned to the webs or legs 60a, 60b in the profile carrier 1, are angled relative to the first region of increased material thickness 4a, which is assigned to the force application surface 40a, preferably angled 90 °, to bring the carrier 1 in its final form.

A further embodiment of a profile carrier 1 according to the invention, which is preferably used as side impact protection in a car, will be described below.

This has, in addition to the first force application surface 40a, from which springs the first web or leg 60a, a second rear force application surface and a third force application surface arranged parallel to the first force application surface 40a, which are interconnected via a second web 60b and a third web 60c. From the third force engagement surface, a fourth ridge or leg extends parallel to the first ridge or leg 60a, resulting in a profile beam having the shape, viewed in cross section, of two (inverted) U's joined together via the second force engagement surface.

For the production of the profile carrier 1, a steel strip 2 with a substantially constant initial thickness one in the first FIGS. 2a and 2b shown pair of rollers 30a, 30b, of which the lower roller 30b has a central portion 50r with a reduced diameter, to which connect on both sides two portions 50v with an enlarged diameter. On the other hand, the upper roller 30a has a larger diameter central portion 50v and two reduced diameter portions 50r adjacent thereto, each of which is followed by a larger diameter portion 50v, as shown in FIG Fig. 2a and 2b is shown. Through the in Fig. 2b indicated rolling of the steel strip 2 is formed in Fig. 2c indicated steel strip 2, which has a total of four work hardened portions 6a, 6b, 6c and 6d with reduced material thickness and three between them arranged portions 4a, 4b and 4c with increased material thickness, of which the middle second portion 4b on the other two portions 4a, 4b opposite side of the profiled steel strip 2 is formed.

Following this, the in Fig. 2c shown steel strip 2 by a forming device, not shown in detail, for example, by means of sequentially and acting at different locations Profilierwalzen transferred to the previously described final form in which the areas 4a, 4b and 4c to the first, second and third force application surface correspond, and Areas 6a to 6c are assigned to the first to fourth bridge.

Finally, in Fig. 3d a further embodiment of a profile carrier according to the invention 1 shown, in which the first force-engaging surface 4a has rounded longitudinal edges on its upper side.

To produce this embodiment of the profile carrier 1 is in the FIGS. 3a to 3b illustrated roller pair 3a, 3b used with an upper roller 3a, in which the transitions from the central portion 5r with reduced diameter to the two adjacent sections 5v with increased diameter continuous, ie not jump in the context of the present application, but continuous or flowing. After rolling off the steel strip ( Fig. 3b ) results in a Fig. 3c shown profiled steel strip 2, which in the subsequent thereto by molding rolls or the like. In the in Fig. 3d shown end shape of the profile carrier is transformed.

LIST OF REFERENCE NUMBERS

1

profile support

2

steel strip

3a

first roller

3b

second roller

4 a

first range of increased material thickness

4 b

second area of increased material thickness

4 c

third range of increased material thickness

5r

Reduced diameter section of the rolls of Fig. 1 and 3

5v

Enlarged diameter section of the rolls of Fig. 1 and 3

6a

first area of reduced material thickness

6b

second area of reduced material thickness

6c

third range of reduced material thickness

6d

fourth range of reduced material thickness

7a

first forming roll

7b

second molding roll

7c

third molding roll

40a

first force application area

40b

second force application area

40c

third force application area

30a

first roller of the embodiment of Fig. 2a

30b

second roller of the embodiment of Fig. 2a

50r

Reduced diameter section of the rolls of Fig. 2

50v

Enlarged diameter section of the rolls of Fig. 2

F

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Claims (7)

1. A method for producing a profiled support (1) made of steel sheet with elevated bending strength which has at least a first force application surface (40a), on which are arranged at least a first and a second crosspiece (60a, 60b), running at an angle to the force application surface (40a), which extend over the length of the profiled support (1), having the following method steps:

   - rolling steel strip (2) with a substantially constant thickness to different thicknesses such that a region (4a) with increased material thickness, which is associated with the first force application surface (40a), and a first and a second region (6a, 6b) with reduced material thickness adjoining this region (4a) on either side, which are associated with the first and second crosspiece (60a, 60b), are produced, and

   - spatially shaping the rolled steel strip (2) such that the regions (6a, 6b) with reduced material thickness in order to form the crosspieces (60a, 60b) run parallel to one another and at a right-angle to the region (4a) with increased material thickness,

   characterised in that
   the rolling of the steel strip (2) to different thicknesses furthermore comprises producing a second region (4b) with increased material thickness adjoining the second region (6b) with reduced material thickness and associated with a second force application surface, and also a third region (6c) with reduced material thickness adjoining it, and in that the shaping comprises the angling of the second region (4b) with increased material thickness at a right-angle to the adjoining second region (6b) with reduced material thickness and the angling of the third region (6c) with reduced material thickness at a right-angle to the second region (4b) with increased thickness, such that a profiled support (1) with a substantially S-like cross-section is produced, and in that the rolling of the steel strip (2) to different thicknesses furthermore comprises the production of a third region (4c) with increased material thickness adjoining the third region (6c) with reduced material thickness and associated with a third force application surface (4c), and also of a fourth region (6d) with reduced material thickness adjoining it, and in that the shaping comprises the angling of the third region (4d) with increased material thickness at a right-angle to the adjoining third region (6c) with reduced material thickness and the angling of the fourth region (6d) with reduced material thickness at a right-angle to the third region (4c) with increased thickness, such that a profiled member with a substantially M-like cross-section is produced.
2. A method according to Claim 1,
   characterised in that
   the transitions between the portions of increased thickness (4a to 4c) and the portions of reduced thickness (6a to 6d) after the rolling of the steel strip (2) and prior to the shaping thereof are sharp-edged.
3. A method according to one of Claims 1 or 2,
   characterised in that
   the transitions between the portions of increased thickness (4a to 4c) and the portions of reduced thickness (6a to 6d) after the rolling of the steel strip (2) and prior to the shaping thereof are constant.
4. A method according to one of the preceding claims,
   characterised in that
   the rolling of the steel strip (2) to different thicknesses takes place by a roller (3a, 3b; 30a, 30b) with at least one open pass, such that the material thickness in at least one region with increased thickness after the rolling corresponds to the material thickness of the steel strip (2) prior to the rolling.
5. A method according to one of the preceding claims,
   characterised in that
   the shaping of the rolled steel strip (2) comprises drawing a collar and/or stretch-forming the material in at least one of the regions (4a to 4c) with increased material thickness.
6. A method according to one of the preceding claims,
   characterised in that
   the steel strip (2) prior to the rolling to different thicknesses is supplied as hot strip.
7. A method according to one of the preceding claims,
   characterised in that
   the supplied steel strip (2) is unwound from a coil, supplied to a rolling means (8) and following this the steel strip (2) which is rolled to different thicknesses is again rolled up to form a coil which is taken to a different location in order to carry out a subsequent shaping operation.

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