DE102010035038A1 - Motor vehicle-bumper bracket, preferably bumper crossbar, sill and/or side impact absorber, comprises longitudinal profile, bar, two legs and flanges - Google Patents

Abstract

Motor vehicle-bumper bracket (1), preferably bumper crossbar, sill and/or side impact absorber, comprises a longitudinal profile (2) with a bar (3) and two legs (4), where their ends are connected to the legs (4, 5) of the flanges and the legs in a common cross-sectional plane exhibit different widths. An independent claim is also included for producing the motor vehicle-bumper bracket, comprising thermoforming a metal plate to an intermediate profile (8) and hardening completely, heat-treating a line-shaped region of the intermediate profile, carrying out a bending operation, and folding the flange on the leg.

Description

The invention relates to a motor vehicle bending beam according to the features in the preamble of patent claim 1 and to methods for its production.

Such a bending beam is used as a motor vehicle component, in particular as a bumper cross member. Furthermore, a concept as a sill or side impact beam is also possible.

Bumpers are installed in motor vehicles both front and rear as standard, to absorb the impact energy of smaller impact processes, so that the actual support structure of the motor vehicle is not damaged as possible. A bumper usually consists of a cross member, which is fixed transversely to the longitudinal members of the motor vehicle frame by inclusion of crash boxes. The cross member serves to initiate the energy resulting from an impact in the crash boxes, where the impact energy is to be converted into deformation work.

From the EP 1 730 002 B1 goes out a bumper with a cross member, which has a U-shaped configured longitudinal profile, with a web and two legs. The ends of the legs are followed by outwardly directed flanges.

In the from the WO 2006/126941 A1 known bumper, the cross member in the central longitudinal section of its arranged on the side facing away from the vehicle web has a bead.

A bending beam for side impact protection is in the DE 20 2005 018 612 U1 described.

The bending beams are usually formed symmetrically in their cross section. In this case, the flanges formed on the ends of the limbs of a bending support or its longitudinal profile generally point in opposite directions, so that the bending beams have outer flanges on both sides or inner flanges on both sides. In a symmetrical cross section of the profile, the centroid of the cross section and the shear center coincide. If it then comes to an asymmetric bending force whose force line of action does not run through the centroid of the profile, there is a risk that the bending beam twisted. The twisting of the bending beam affects its effect, especially in the recording of load paths and can lead to adverse movements. When using the bending support, for example as a bumper cross member, the twisting can lead to a sliding of the motor vehicle under an obstacle.

The invention is therefore an object of the invention to provide a load behavior improved cross member, which does not twist or less at an asymmetric bending force acting and to show an advantageous method for its production.

The solution of the objective part of the task consists in a motor vehicle bending beam according to the features of claim 1.

Advantageous embodiments of the motor vehicle bending beam according to the invention are the subject of the dependent claims 2 to 7.

Two independent solutions of the procedural part of the task are characterized in claims 8 and 9.

The motor vehicle bending beam has an open longitudinal profile with a central web and two legs, with end flanges adjoining the legs. According to the invention, the legs have different widths in a common cross-sectional plane.

Preferably, the flanges are oriented in the same direction. As a result, one flange is facing inwards (inner flange) in the cross-section of the profile, while the other flange is directed outwards (outer flange).

With a one-sided inner flange and a leg width ratio not equal to 1, the shear center of the cross section shifts so that an asymmetrically acting bending force causes no or only a slight rotation of the bending beam. The bending beam consequently twists less so that its function is maintained stable. In the case of a bumper cross member, undercarriage of a vehicle under an obstacle can thus be avoided or reduced.

Width of a leg is to be understood as meaning the extension of the leg measured transversely to the longitudinal extension of the bending support. Preferably, the ratio of the width of the first broader leg to the width of the second shorter leg is sized between 1.2: 1 and 2: 1.

In an embodiment which is advantageous for practice, the flange on the first, broader leg is directed in the direction of the central longitudinal axis, whereas the flange on the second, shorter leg is directed away from the central longitudinal axis. The inner flange is thus located on the wider leg, whereas the outer flange is provided on the shorter or less wide second leg.

The motor vehicle bending beam or its longitudinal profile is advantageously made of high-strength steel and is preferably thermoformed and hardened, in particular press-hardened.

Furthermore, the longitudinal profile of the motor vehicle bending support sections having different from each other hardness. This can support a component-optimized design of the deformation behavior of the motor vehicle bending beam.

Furthermore, at least one bead can be formed in the web of the longitudinal profile. Due to the nature and arrangement of the beads, the longitudinal profile can be reinforced and / or tailored to the load behavior. The web, which forms the front surface as a bumper cross member when using the motor vehicle bending beam, preferably has a height of greater than or equal to 75 mm. For the stiffness behavior of the motor vehicle bending support is advantageous if the ratio of the height of the web to the width of the wider flange is between two 2: 1 and 4: 1 dimensioned.

To produce a motor vehicle bending beam according to the invention, a metal plate, in particular a steel plate made of uncured, hot-workable steel is heated to a hardening temperature above the austenitizing temperature and formed into an intermediate profile. Time-parallel or in the immediate connection, preferably clamped in the press tool, there is a compensation of the intermediate profile, in which the intermediate profile is completely cured. Subsequently, the intermediate component is heat-treated along a line-shaped region and annealed again in this region in order to allow a local deformation. Along the line-shaped area, a bending operation is then carried out and a flange is folded on a leg of the longitudinal profile.

Alternatively, a metal plate may be hot-formed into an intermediate profile and hardened only partially so that a longitudinal portion on one leg of the intermediate member is left soft or at least lower in hardness than an adjacent portion. Thereafter, a bending operation is performed in the softer length portion and the length portion is folded to a flange on the leg.

The heating of the metal plate and / or the intermediate profile is preferably carried out inductively. Inductive heating is efficient and reliable and can also be used in particular for precise heating of a linear region on the intermediate component.

The invention is described below with reference to schematic drawings. Show it:

1 in a schematic perspective view of a motor vehicle bending beam according to the invention;

2 a vertical cross section through the motor vehicle bending beam according to the 1 ;

3 technically simplifies two steps in the manufacture of a motor vehicle bending beam according to the invention and

four again technically simplified two steps in an alternative manufacturing variant.

1 shows a simplified motor vehicle bending beam according to the invention 1 in the form of a bumper crossmember. The motor vehicle bending beam 1 has a one-sided open longitudinal profile 2 on which a central in image plane vertically oriented jetty 3 owns, with a first upper leg four and a second lower leg 5 , End to the thighs four . 5 each closes a flange 6 . 7 at.

In the 1 are left and right at the end of the longitudinal profile 2 with L clamping called the storage or clamping of the bending beam 1 within a motor vehicle.

In particular, based on the 2 you realize that the thighs four . 5 , measured in a common cross-sectional plane QE, have different widths b1 and b2. The first upper leg four has a width b1 that is greater than the width b2 of the lower side leg 5 ,

Basically, the ratio of the width b1 of the first leg four to the width b2 of the second leg 5 between 1.2: 1 and 2: 1.

Furthermore, the flanges have 6 . 7 in the same direction R. The flange 6 on the first leg four is as an inner flange in the direction of the central longitudinal axis MLA of the longitudinal profile 2 directed, whereas the flange 7 on the second leg 5 is directed away from the central longitudinal axis MLA outwards and so forms an outer flange.

The centroid of the cross section is in the 2 marked with Sp. Furthermore, in the 2 the shear center of the profile is denoted by Sm. In the 1 and 2 Furthermore, a force F is shown. The force F acts asymmetrically, so that its line of action does not run through the centroid Sp of the cross-sectional profile.

Due to the design of the longitudinal profile 2 with one-sided inner flange 6 and a ratio of the width b1 of the legs four to the width b2 of the thigh 5 which is greater than 1, the shear center Sm of the cross section shifts away from the centroid Sp. One recognizes in the 2 in that the centroid Sp and the shear center Sm do not coincide, the shear center Sm being above the centroid Sp in the direction of the web 3 is offset. As a result, in the case of an asymmetrically acting bending force F, a rotation of the motor vehicle bending beam can occur 1 avoided or at least greatly reduced. In the 2 is a dotted line moving the longitudinal profile 2 illustrated with an asymmetrically acting force F. The longitudinal profile 2 shifts to the left in the image plane without the longitudinal profile twisting. This leads to an improvement of the load behavior of the motor vehicle bending beam 1 , A sliding under a motor vehicle under an obstacle is avoided, or at least the risk that it comes reduced.

Preferably, the longitudinal profile exists 2 made of a high-strength steel and is shaped warm.

Two production variants are based on the 3 and four explained.

In the procedure according to the 3 a steel plate of uncured, hot formable steel is heated to a hardening temperature above the Austenitisierungstemperatur the material and in a first steps (step 1 ) to an intermediate profile 8th formed and tempered, whereby the intermediate profile is completely hardened. Subsequently, the intermediate component 8th along a linear area 9 heat treated, leaving the material in this area 9 is soft annealed again. In a second step (step 2 ) is then on the intermediate component 8th along the linear area 9 carried out a bending operation and so the upper flange 6 on the longitudinal profile 2 folded.

In the procedure, as based on the four explains, a steel plate becomes an intermediate profile 10 warm formed and only partially in the area indicated by dashed lines 11 hardened (step 1 ). One recognizes that a length section 12 on the upper thigh 4 ' of the intermediate component 10 remains uncured and is left soft. Subsequently, a bending operation in the uncured length section 12 performed and the longitudinal section 12 at the transition Ü to the hardened area 11 in the longitudinal direction of the longitudinal profile 2 inside to the flange 6 is folded.

LIST OF REFERENCE NUMBERS

1

Automotive bumper bracket

2

longitudinal profile

3

web

4

first leg

4 '

with thighs

5

second leg

6

Flange (inner flange)

7

Flange (outer flange)

8th

intermediate profile

9

line-shaped area of 8th

10

intermediate profile

11

Area

12

longitudinal section

b1

width

b2

width

F

force

MLA

central longitudinal axis

R

direction

sm

Shear center

sp

Centroid

QE

Cross-sectional plane

L

storage

Ü

crossing

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1730002 B1 [0004]
• WO 2006/126941 A1 [0005]
• DE 202005018612 U1 [0006]

Claims (10)

Automotive bending beam ( 1 ), in particular bumper cross member, sill or side impact beam, which has a longitudinal profile ( 2 ) with a bridge ( 3 ) and two thighs ( four . 5 ), wherein the ends of the legs ( four . 5 ) Flanges ( 6 . 7 ), characterized in that the legs ( four . 5 ) have different widths (b1, b2) in a common cross-sectional plane (QE). Motor vehicle bending beam according to claim 1, characterized in that the ratio of the width (b1) of the first leg ( four ) to the width (b2) of the second leg ( 5 ) is dimensioned between 1.2: 1 and 2: 1. Motor vehicle bending beam according to claim 1 or 2, characterized in that the flanges ( 6 . 7 ) are oriented in the same direction (R). Motor vehicle bending beam according to claim 3, characterized in that the flange ( 6 . 7 ) on the first, wider leg ( four ) in the direction of the central longitudinal axis (MLA) of the longitudinal profile ( 2 ) and the flange ( 6 . 7 ) on the second, shorter leg ( 5 ) is directed away from the central longitudinal axis (MLA). Motor vehicle bending beam according to one of claims 1 to 4, characterized in that the longitudinal profile ( 2 ) is thermoformed. Motor vehicle bending beam according to one of claims 1 to 5, characterized in that the longitudinal profile ( 2 ) Has sections with mutually different hardnesses. Motor vehicle bending beam according to one of claims 1 to 6, characterized in that in the web ( 3 ) of the longitudinal profile ( 2 ) is formed a bead. Method for producing a motor vehicle bending support according to one of claims 1 to 7, characterized in that a metal plate to an intermediate profile ( 8th ) is thermoformed and fully cured, after which a line-shaped area ( 9 ) of the intermediate profile ( 8th ) is heat treated and after the heat treatment at the intermediate profile ( 8th ) along the line-shaped area ( 9 ) performed a bending operation and a flange ( 6 ) on a leg ( four ) is folded. Method for producing a motor vehicle bending support according to one of claims 1 to 7, characterized in that a metal plate to an intermediate profile ( 10 ) is thermoformed and partially cured, wherein a longitudinal section ( 12 ) on a leg ( 4 ' ) of the intermediate profile ( 10 ) has a lower hardness than an adjacent area ( 11 ) of the intermediate profile ( 10 ) and then the length section ( 12 ) by a bending operation to a flange ( 6 ) on the thigh ( four ) is folded. A method according to claim 8 or 9 characterized. the heating of the metal plate and / or the intermediate profile takes place inductively.

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