Bumper beam

1. A bumper beam for a vehicle, which at least in attachment regions ( 20 ) of said bumper beam is of generally U-shaped cross-section with a crown ( 12 - 16 ) pointing outwards, said crown including a central flange and two webs extending from said central flange in a direction towards said vehicle, characterised in that the crown has a larger profile height than profile width at the attachment regions and a smaller profile height than profile width at a longitudinal central portion of said bumper beam such that the profile height of the bumper beam is larger at the attachment regions than at the longitudinal center, said bumper beam being oriented asymmetrically in a vertical direction relative to the longitudinal direction of extension of said bumper beam, and said bumper beam has in each said attachment region ( 20 ) a single transverse metal bulkhead ( 25 ) fastened between sides ( 12 , 13 ) of the crown and running generally in the longitudinal direction of the vehicle for reducing tilting of the bumper beam relative to the vehicle when the bumper beam is subjected to an impact force during a collision, each said transverse bulkhead being attached to said webs and arranged such that an intermediate portion of each said transverse bulkhead is curved inwardly away from at least one of said webs and does not directly abut against said at least one of said webs for initiating deformation of said transverse bulkhead during a collision.

2. A bumper beam according to claim 1 , characterised in that said bumper beam is of hat-shaped cross-section, the height of which is greatest in the attachment regions, and said bumper beam has planar side flanges ( 17 , 18 ) with fastening holes ( 21 - 23 ) for bolts.

3. A bumper beam according to claim 2 , characterised in that, as seen along the beam, each transverse bulkhead ( 25 ) is situated between two fastening holes ( 21 , 22 ).

4. A bumper beam according to claim 1 , characterised in that each said transverse bulkhead ( 25 ) is welded to the top of the crown and to the base of the crown by welds ( 26 - 29 ) but has no welds in an intermediate portion.

5. A bumper beam according to claim 4 , characterised in that said intermediate portion ( 31 ) with no welds is at a distance from the crown's sides ( 15 , 16 ).

6. A bumper beam according to claim 2 , characterised in that each said transverse bulkhead ( 25 ) is welded to the top of the crown and to the base of the crown by welds ( 26 - 29 ) but has no welds in an intermediate portion.

7. A bumper beam according to claim 3 , characterised in that each said transverse bulkhead ( 25 ) is welded to the top of the crown and to the base of the crown by welds ( 26 - 29 ) but has no welds in an intermediate portion.

8. A bumper beam according to claim 2 , characterised in that each said transverse bulkhead ( 25 ) is welded to the top of the crown and to the base of the crown by welds ( 26 , 29 ) but has no welds in an intermediate portion, said intermediate portion ( 31 ) with no welds is at a distance from the crown's sides ( 15 , 16 ).

9. A bumper beam according to claim 3 , characterised in that each said transverse bulkhead ( 25 ) is welded to the top of the crown and to the base of the crown by welds ( 26 , 29 ) but has no welds in an intermediate portion, said intermediate portion ( 31 ) with no welds is at a distance from the crown's sides ( 15 , 16 ).

10. A bumper beam according to claim 1 , characterised in that said crown defines a central groove ( 14 ) extending longitudinally therewith.

11. A bumper beam according to claim 1 , wherein said bumper beam widens asymmetrically downwardly in a direction from said attachment regions towards the longitudinal center of the bumper beam for reducing tilting of the bumper beam relative to the vehicle when a lower portion of the bumper beam is subjected to an impact force during a collision.

12. A bumper beam according to claim 1 , characterised in that the height of said bumper beam is less than two thirds of the maximum height of the webs at the center of the bumper beam.

13. A bumper beam according to claim 10 , characterised in that the central groove is defined in the central flange.

14. A bumper beam according to claim 1 , characterised in that the bumper beam has side flanges ( 17 , 18 ) extending from said webs ( 15 , 16 ), said side flanges being bent towards said central flange between said attachment regions of said bumper beam.

15. A bumper beam for a vehicle, which at least in attachment regions ( 20 ) of said bumper beam is of generally U-shaped cross-section with a crown ( 12 - 16 ) pointing outwards, said crown including a central flange and two webs extending from said central flange in a direction towards said vehicle, characterised in that the crown has a larger profile height than profile width at the attachment regions and a smaller profile height than profile width at a longitudinal central portion of said bumper beam such that the profile height of the bumper beam is larger at the attachment regions than at the longitudinal center, said bumper beam has in each said attachment region ( 20 ) a single transverse metal bulkhead ( 25 ) fastened between sides ( 12 , 13 ) of the crown and running generally in the longitudinal direction of the vehicle, each said transverse bulkhead being attached to said webs and arranged such that an intermediate portion of each said transverse bulkhead is curved inwardly away from at least one of said webs and does not directly abut against said at least one of said webs for initiating deformation of said transverse bulkhead during a collision.

16. A bumper beam according to claim 15 , characterised in that said bumper beam is oriented asymmetrically in a vertical direction relative to the longitudinal direction of extension of said bumper beam.

17. A bumper beam according to claim 15 , characterised in that said bumper beam is oriented symmetrically in a vertical direction relative to the longitudinal direction of extension of said bumper beam.

18. A bumper beam according to claim 15 , characterised in that the height of said bumper beam is less than two thirds of the maximum height of the webs at the center of the bumper beam.

19. A bumper beam according to claim 15 , characterised in that said crown defines a central groove ( 14 ) extending longitudinally therewith.

20. A bumper beam according to claim 19 , characterised in that in that the central groove is defined in the central flange.