IMPACT BEAM AND METHOD OF MANUFACTURING THE SAME

Abstract: An impact beam comprising a close one chamber configurated member (1) exhibits over a predetermined part(s) of its longitudinal extension inwardly protruding indentations (15) on at least two interfacing walls of the members.

Description: "IMPACT BEAM AND METHOD OF MANUFACTURING THE SAME" The present invention relates to an elongated impact beam, and more particularly to a bumper beam for vehicles, and a method of manufacturing the same. The bumper beam applied nowadays as a front or rear impact protection in automotive vehicles is generally curved or bent along its longitudinal extension for several reasons. This curved configuration is not only desirable for the aesthetic impression of private cars or provision of more space in the central area to accommodate e.g. the vehicle's radiator. First of all, this particular curved shape allows instant in deflection of the beam when exposed to an impact, e.g. collision, first during the elastic phase and later on the following plastic deformation depending on the magnitude of the impact (speed of the car) without damaging structural parts behind the beam. This combined demand to the beam construction, coping with low speed impacts without permanent deformation (speed below 4 km/h) and simultaneously absorbing energy in a controlled manner at high speeds, is an engineering challenge. Customarily the bumper beams are designed as closed chamber shapes provided internally/- externally with reinforcing means or multichamber shapes, where the internal webs/partition walls represent the reinforcement. However, such known solutions, apart from increasing the weight of the beam, require additional manufacturing activities and thus increase substantially the manufacturing costs. It is an objective of the present invention to provide a novel impact beam exhibiting increased buckling resistance and lateral stability of the beam and thus thereby to increase the energy absorption performance of the beam. A further objective is to improve/maximize the elastic energy absorption of the beam. Still another objective of the invention is to provide a one piece impact beam having integrated attachment means exhibiting minimal material consumption, thereby resulting in considerable cost and weight savings. These and other objectives and advantageous special features according to the present invention are met by providing a novel method of manufacturing an impact beam and the resulting beam as defined in the accompanying patent claims 1 and 6, respectively. The invention will now be described in details by the way of preferred embodiments referring to the attached drawings, Figs. 1 -4, where Fig. 1 shows schematically in a perspective view a preferred embodiment of the impact beam according to the invention, Fig. 2 illustrates the different cross-sectional configuration along the longitudinal extension of the beam, Fig. 3 is a diagram impact force/displacement illustrating the difference between the energy absorption performance of the impact beam provided according to the present invention compared to a reference beam, and Fig. 4 shows another embodiment of an impact beam. Referring to Figure 1 illustrating schematically in a perspective view the impact beam embodied as a bumper beam, the beam comprises one chamber configurated member 1 being preferably fabricated of a light weight material such as high strength Al-alloy starting from a straight hollow shape member being extruded in a conventional manner. The beam exhibits a central part 11 of generally single closed chamber configuration illustrated in a cross-sectional view taken along lines A-A in the Figure as rectangular (other basic shapes than the shown rectangular one, e.g. oval, could also be applied). After the bending operation the two lateral parts of the beam 12,13 are exposed to a deformation (by any conventional working means) providing the interfacing top and bottom walls of the beam with inwardly extending indentations 15. According to a preferred embodiment of the bumper beam the depth of the indentations varies along such provided locally inverted walls, in this case successively increasing towards the ends of the beam as illustrated in vertical cross-sectional views taken along lines D-D and E-E in the Figure, thereby providing a more flexible beam. Figure 2 illustrates in enlarged schematical cross-sectional views the variations in the inwardly extending indentations 15 starting from the rectangular cross-section a) through the locally inverted (concave) configuration of the interfacing top/bottom walls b) into the deep indentations 15 in c). Tests conducted on beams provided according to the present invention made of high strength Al-alloy from 7000 series show a remarkable lateral stability and substantial increase in the energy absorption exhibiting a different force/displacement curve compared to the reference beams. Figure 3 shows such diagram illustrating a fundamental difference between curves A (beams provided with inverse walls according to the present invention) and B (reference beams). While curve B exhibits typical fall in force required for further displacement due to an uncontrolled deformation of the top/bottom walls of the beam (illustrated in the Figure by cross-sectional deformation after approx. 80 mm displacement) the curve A shows different behaviour keeping nearly constant force level during further displacement beyond 80 mm. The sudden increase of the force required for further plastic deformation is a result of a transformation from one chamber to a double chamber configuration of the cross-sectional configuration of the beam by abutting of the antagonistically inverted wall indentations as illustrated in the Figure. Figure 4 illustrates another embodiment of the bumper beam exhibiting where also the front wall of the beam is provided with an inwardly extending indentation 15 as shown in a cross-sectional view. In both illustrated embodiments of the bumper beam the ends of the beams are advantageously reshaped three dimensionally to provide integrated attachment means 18 for a grid parallel attachment to e.g. the front/rear members of the vehicle frame construction. Fig. 1 a illustrates schematically in details in a rear view, a top view and a perspective view, respectively, the freedom with regard to the material (flow) distribution thanks to provision of the indentations 18. A further advantage is a non-obstructed access to the one chamber cavity of the beam from the ends with forming tools, mandrils etc. The present invention is not limited to the shown examples and bumper beams. An impact beam provided in accordance with the above described principles can be applied as impact protection incorporated e.g. as reinforcing door beam or reinforcement in a space frame construction of a vehicle body. The provision of inwardly protruding indentations over a predetermined part of the longitudinal extension of the beam can also cover the whole extension of the beam if appropriate.

Claims: Claims 1. Impact beam, particularly for automotive vehicles, comprising a close one chamber configurated member (1) exhibiting over a predetermined part(s) of its longitudinal extension inwardly protruding indentations (15) on at least two interfacing walls of the member the indentations (15) ensuring controlled plastic deformation upon an impact resulting ultimately in a transformation of the one chamber cross-sectional configuration of the beam towards a double chambered configuration by abutting of the antagonistical indentations (15). 2. The impact beam according to claim 1 , characterized in that the beam is a bumper beam comprising a central part (11) having a closed single chamber configuration and two lateral parts (12,13) having the interfacing top and bottom walls of the inverted configuration. 3. The bumper beam according to claim 2, characterized in that the lateral parts (12,13) exhibit variation in the depth of the indentations along the locally inverted walls, thereby giving a more flexible beam. 4. The bumper beam according to claim 3, characterized in that the depth of the indentation is successively increasing towards the ends of the beam. 5. The bumper beam according to one or more preceding claims, characterized in that the bumper is one single piece beam integrating also grid parallel attachment means (18). Method of manufacturing an impact beam for automotive vehicles comprising steps of - providing a single close chamber member, - bending of the member involving three dimensional deformation into the desired configuration of the beam, and - preforming of at least two interfacing walls of the member over a predetermined extension of the member providing inwardly protruding indentations.

Inventors: HOEILAND THORBJOERN, LUNDBERG ANDERS, PEDERSEN ROALD HELLAND, HOEILAND, THORBJOERN, LUNDBERG, ANDERS, PEDERSEN, ROALD, HELLAND
Applicants: HOEILAND THORBJOERN, LUNDBERG ANDERS, NORSK HYDRO AS, PEDERSEN ROALD HELLAND, HOEILAND, THORBJOERN, LUNDBERG, ANDERS, NORSK HYDRO ASA, PEDERSEN, ROALD, HELLAND
Application year: 2000
Main classification: B60R19
IPC codes: B60J5, B60R11, B62D21, F16F7