TUBULAR SPRING FOR MOTOR VEHICLES, AND A METHOD FOR PRODUCING A TUBULAR SPRING

Abstract

A tubular spring, such as a coil spring, a torsion-rod spring, and/or a stabilizer for a motor vehicle, may include at least one metal tube element having a tube internal cross section, a tube internal diameter, a tube external diameter, a tube internal wall, and a tube wall thickness. At least one metal foam may be disposed in the tube internal cross section of the at least one metal tube element of the tubular spring in at least one part-region. In particular, the metal foam may be connected in an at least partially materially integral manner to the tube internal wall of the metal tube element. The at least one metal tube element may have an at least partially martensitic structure.

Claims

1.-12. (canceled)

13. A tubular spring comprising: a metal tube element having a tube internal cross section, a tube internal diameter, a tube external diameter, a tube internal wall, and a tube wall thickness, wherein the metal tube element has an at least partially martensitic structure; and a metal foam disposed in the tube internal cross section of the metal tube element of the tubular spring in at least one part-region.

14. The tubular spring of claim 13 configured as a torsion-rod spring.

15. The tubular spring of claim 13 configured as a coil spring.

16. The tubular spring of claim 13 configured as a stabilizer.

17. The tubular spring of claim 13 wherein the metal foam is connected in an at least partially materially integral manner to the tube internal wall of the metal tube element.

18. The tubular spring of claim 13 wherein a ratio of the tube external diameter relative to the tube wall thickness is more than 8.

19. The tubular spring of claim 13 wherein the metal foam has a density of less than 1 g/cm.sup.3.

20. The tubular spring of claim 13 wherein the metal tube is at least partially formed so as to be a tubular spring that is configured so as not to be fully rectilinear.

21. A method for producing a tubular spring that is foamed in at least one part-region, the method comprising: providing a preliminary material composition comprising a metal component having a melting temperature, and an expanding agent component; providing a tubular spring comprising a metal tube element having a tube internal cross section, a tube internal diameter, a tube external diameter, a tube internal wall, and a tube wall thickness; inserting the preliminary material composition into the metal tube element of the tubular spring, wherein the metal tube element is filled completely or in the at least one part-region; and tempering the metal tube element as filled completely or in the at least one part-region, wherein the tempering comprises heating the metal tube element at least to a hardening temperature, wherein the hardening temperature is above a minimum re-crystallization temperature of the metal tube element, wherein the hardening temperature is equal to or higher than the melting temperature of the preliminary material composition, wherein the preliminary material composition foams while heating the metal tube element such that the metal tube element includes a metal foam in the at least one part-region, quenching the metal tube element to a first cooling temperature that is below the minimum re-crystallization temperature of the metal tube element, wherein an at least partially martensitic structure is set in the metal tube element, re-heating the metal tube element to a first tempering temperature that is lower than an austenite start temperature of the metal tube element, and cooling the metal tube element to a second cooling temperature that is lower than the first tempering temperature, so as to form an at least partially materially integral connection in the at least one part-region between the tube internal wall of the metal tube element and the metal foam of the metal tube element.

22. The method of claim 21 wherein the metal tube element that is provided includes a ferritic pearlitic structure, at least in part.

23. The method of claim 21 wherein at least one of the metal tube element that is provided before insertion of the preliminary material composition or the metal tube element that includes the metal foam and has been tempered is configured so as not to be fully rectilinear, the method further comprising forming the metal tube element in the at least one part-region.

24. The method of claim 23 wherein the forming of the metal tube element in the at least one part-region is cold-forming and is performed at a cold-forming temperature after the metal tube element is tempered, wherein the cold-forming temperature is below the minimum re-crystallization temperature of the metal tube element.

25. The method of claim 23 wherein the forming of the metal tube element in the at least one part-region is cold-forming and is performed at a cold-forming temperature after the metal tube element is tempered, wherein the cold-forming temperature is below the austenite start temperature of the metal tube element.

26. The method of claim 23 wherein the forming of the metal tube element in the at least one part-region is hot-forming and is performed at a hot-forming temperature prior to the tempering of the metal tube element, wherein the hot-forming temperature is above the minimum re-crystallization temperature of the metal tube element.

27. The method of claim 23 wherein the forming of the metal tube element in the at least one part-region is hot-forming and is performed at a hot-forming temperature prior to the tempering of the metal tube element, wherein the hot-forming temperature is above the austenite start temperature of the metal tube element.

28. The method of claim 21 wherein a density of the metal foam in the metal tube element is less than 1 g/cm.sup.3.

29. The method of claim 21 wherein a density of the metal foam in the metal tube element is less than 0.6 g/cm.sup.3.

30. The method of claim 21 wherein a density of the metal foam in the metal tube element is in a range from 0.1 to 0.5 g/cm.sup.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The tubular spring according to the invention will be explained by means of the drawings in which

[0049] FIG. 1 schematically shows variously formed tubular springs according to the prior art;

[0050] FIG. 2 schematically shows an oblique view of a metal tube element of a tubular spring according to the prior art; and

[0051] FIG. 3 schematically shows a cross section of a foamed metal tube element of a tubular spring according to embodiments of the invention.

[0052] Variously formed tubular springs 1 according to the prior art are illustrated and marked a) to c) in FIG. 1. A torsion-rod spring 2 is illustrated as a). The marking b) illustrates a coil spring, and c) illustrates a stabilizer 4.

[0053] An oblique view of a metal tube element 5 of the tubular spring 1 according to the prior art is illustrated in FIG. 2. The metal tube element 5 has a tube internal cross section 6 having a tube internal diameter DI, a tube external diameter DA, a tube internal wall 7, and a tube wall thickness W. The tube internal cross section 6 is not foamed.

[0054] A cross section of the foamed metal tube element 5 of a tubular spring 1 according to one embodiment of the invention is schematically illustrated in FIG. 3. At least the metal foam 8 is disposed within the tube internal cross section 6 in at least one part-region. The metal tube element 5 according to the invention has the tube internal cross section 6 having the tube internal diameter DI, the tube external diameter DA, the tube internal wall 7 and the tube wall thickness W. The metal foam 8 is illustrated as a variable porous structure.

INDUSTRIAL APPLICABILITY

[0055] Tubular springs, in particular as a coil spring, a torsion-rod spring, and/or a stabilizer of the type described above are used in the production of motor vehicles, in particular of suspension systems of the motor vehicles.

LIST OF REFERENCE SIGNS

[0056] 1=Tubular spring [0057] 2=Torsion-rod spring [0058] 3=Coil spring [0059] 4=Stabilizer [0060] 5=Metal tube element [0061] 6=Tube internal cross section [0062] 7=Tube internal wall [0063] 8=Metal foam [0064] DA=Tube external diameter of the metal tube element [0065] DI=Tube internal diameter of the metal tube element [0066] W=Tube wall thickness