WO2004030996A1

WO2004030996A1 - Beam

Info

Publication number: WO2004030996A1
Application number: PCT/NO2003/000331
Authority: WO
Inventors: Lars Moen; Sindre Seim
Original assignee: Norsk Hydro Asa
Priority date: 2002-10-03
Filing date: 2003-10-03
Publication date: 2004-04-15
Also published as: NO20024789D0; AU2003269733A1

Abstract

A beam (1) where at least one of the end sections (6) of the beam (1) is provided with a protrusion (5) and where the protrusion (5) is formed as an integral part of the front wall (2) of the beam.

Description

Beam

The present invention relates to a beam and especially a structural beam for use in crash protection of a vehicle where the beam is situated in the front or rear part of the vehicle, consisting of an extruded and further formed aluminium profile having a cross section forming a front wall and two side walls provided with arrangements enabling it to be attached to the structure of the vehicle, such as the frame.

It is common practice to extrude hollow profiles and shape these into beams used as crash protection on vehicles. The beam can be mounted on crash boxes, which are connected to the structure of the vehicle, or it may be mounted directly on the side members of the car.

This is known from EP 602 138 B1 which describes a structural beam. The beam is often bent to follow the sweep of the front line of the car. The beam will thereby be situated close behind the plastic facia. As an extra energy absorbing means, polymer foam might fill the intermediate space between the bumper and the facia covering the inner structure of the vehicle.

During a crash situation, the beam will absorb energy through deforming and bending inwards into the vehicle. The amount of energy absorbed by the beam before other parts of the vehicle are affected is thereby limited by the free space given for the beam to deform into. As the beam of EP 602 138 B1 is bent into abutment with the further vehicle structure, the limit of energy abortion of the beam is reached.

The object of the invention is to provide a better crash behaviour by enabling the structural beam to absorb more energy. This is done by modifying the cross section at the end section of the beam. The front wall of the beam is protruded out from the central axis of the beam, thereby forming a shape extending more forward than the rest of the beam. The protrusion is preferably situated close to the beam extremity in the end section of the beam.

If the beam is hit by an impacting object, generating a force pushing the central section of the beam into the vehicle, the end sections of the beam will be bent outwards. The protrusions on the end section of the beam will then meet the object hitting the vehicle. The deformation of the protrusions will compensate for the further deformation of the beam into the vehicle, thereby absorbing extra deformation energy in the beam without affecting the load carrying structure of the vehicle.

In a pendulum crash where forces are affecting the corners of the vehicle, the headlight arrangements of the vehicle will be protected as the protrusions are deforming before the headlight arrangements are affected.

Furthermore, the contact forces will be balanced in the fixations. As the central section situated on one side of the fixation point is bent into the vehicle, the end section of the beam will be bent outwards from the vehicle. Thereby the force acting on the fixation point due to deformation in the central section of the beam will be balanced by a force acting on the fixation point due to the forces acting on the protrusions on the end section of the beam. As a consequence, the bending moment (around the car's vertical axis) introduced on the fixations will be lower than on prior art beams.

The beam will now be further explained by way of examples and with reference to figures, where

Fig. 1 shows a beam of prior art,

Fig. 2 shows a beam provided with a protrusion,

Fig. 3 shows a cross section of an undeformed section of a beam,

Fig. 4 shows a cross section of a deformed section of a beam, Fig. 5 shows graphically the energy absorbing ability of a beam of prior art and a beam provided with protrusions.

Fig. 1 shows a beam 1' of prior art. The hollow profile of the beam consists of a front wall 2', a back wall 3' and the two side walls 4' of which only one can be seen on Fig. 1. The beam 1' is formed to follow the outer shape of the vehicle. The front wall 2' of the beam will thereby make an even outer curve as can be seen on Fig. 1. The beam can be attached to crash boxes which again are attached to the chassis of the vehicle or directly on the vehicle structure.

Fig. 2 shows a beam 1 with protrusions 5 according to the invention. The beam is formed to follow the outer curve of the vehicle. The front wall 2 of the beam will thereby form a slope in the central section 7. At the end sections 6, the front wall is lifted up from the central axis C-C of the beam, forming a protrusion 5 integrated in the front wall surface.

The end section 6 of the beam 1 will protrude from the rest of the structure in an area where energy absorbing foam is not considered important for the protection of pedestrians. It is assumed that a body hitting the vehicle near the corner will slide off the vehicle. This gives a possibility to utilise the front wall 2 of the beam 1 to protect the headlight arrangement and any other equipment situated in the corner area of the vehicle.

Fig. 3 shows the cross section of a beam 1 , marked as A-A on Fig. 2. Due to the extrusion process it is possible to form a cross section having canals, flanges or other forms found suitable. The flanges 8 on the beam 1 will be advantageous in the process of forming the protrusions 5. This because the protrusions 5 are formed by the straightening of the flanges 8. In this manner the side walls 4 will not become thinner due to forming of the protrusions 5. Optionally extra material can be made available by forming extra canals or flanges in the profile during the extrusion process. This will enable the forming of protrusions without limitations due to lack of material in the walls being expanded.

Fig. 4 shows the cross section of the profile at the end section 6 of the beam, marked as B-B on Fig. 2. The front wall 2 is drawn forwards, thereby narrowing the beam 1.

Fig. 5 shows the results in a test measuring the energy absorbing ability of a beam of prior art without protrusions and of a beam provided with protrusions according to the invention. The test used is a standard AZT insurance-test where the beam is mounted on a vehicle which impacts into a barrier. The energy absorbed is measured by measuring the force and barrier intrusion used to deform the beam.

The deformation ability at the start of the impact is approximately equal. This is the deformation behaviour of the beams as the central sections of the beams are bent inwards to the vehicle. When the protrusions 5 at the end section 6 of the beam according to the invention gets into contact with the object deforming the beam, the amount of energy absorbed is greatly increased compared to the beam having an even front wall. The curve showing the force and barrier intrusion of the beam provided with protrusions 5 shows an extra leap before the collapse of the beam.

The integrated protrusions in the front wall of the beam will give a better opportunity to pre-calculate the energy absorbing ability of the beam. This eases the construction process and improves the constructors' ability to form a beam giving the best deformation protection obtainable. The integrated protrusions according to the invention may also be used on any types of extruded profiles used for vehicle protection beams. The beams might have side walls being curved on parts of the sections, forming intrusions, canals of protruding along the axis of the beam.

The back wall of the beam might be shaped independently of the protrusions in the front wall. This can also be done within the scope of the invention.

It should furthermore be noted that the integrated protrusions can also be formed in an open profile. The protrusions are not directly affected by the back wall in any way. It is therefore possible to integrate protrusions in any front wall beam.

Claims

1. A beam (1) and especially a structural beam for use in crash protection of a vehicle where the beam is situated in the front or rear part of the vehicle, the beam consisting of an extruded and further formed aluminium profile having a hollow cross section forming a front wall (2) and two side walls (4), provided with arrangements enabling it to be attached to the structure of the vehicle, characterised in that at least one of the end sections (6) of the beam (1) is provided with a protrusion (5).

2. A beam (1) according to claim 1 , characterised in that the at least one protrusion (5) is arranged in the front wall (2) of the beam.

3. A beam (1 ) according to any of the preceding claims 1 or 2, characterised in that the at least one protrusion (5) is formed as an integral part of the beam (1).

4. A beam (1) according to any of the preceding claims 1-3, characterised in that the beam is provided with a back wall (3), thereby forming a closed hollow profile.

5. A beam according to claims 1 -4, characterised in that at least one flange (8) is extending from the beam following the central axis of the beam (1).

6 A beam (1 ) according to any of the preceding claims 1 -5, characterised in that canals are provided in at least one of the walls forming the beam (1) following the central axis of the beam (1).

7. A beam (1) according to any of the preceding claims 1-6, characterised in that at least one protrusion (5) is formed of a separate part being attached to the front wall (2) of the beam (1).