Gas pressure container and tube element for an airbag system, and method for producing same

Abstract

A gas pressure container for an airbag system of a motor vehicle is disclosed having a tube element with a high bursting resistance when internal pressure is being applied. The tube element includes a steel alloy and a first longitudinal portion of the tube element has a tensile strength Rm,.sub.11 higher than (>) 800 MPa, a transition temperature Tu,.sub.11 of at least 40 C., and an outer circumference U1. The tube element also includes at least one second longitudinal portion and/or additional longitudinal portions, which extend axially from the first longitudinal portion. The second longitudinal portion or the additional longitudinal portions and the first longitudinal portion are formed from a seamless or welded single-piece tube made of a uniform material, and more specifically from a hot-rolled or cold-drawn tube.

Claims

1. A gas pressure container for an airbag system of a motor vehicle, the gas pressure container comprising: a tube element with high bursting resistance when internal pressure is applied, wherein the tube element is of a steel alloy, wherein the tube element includes at least one first longitudinal portion which comprises a tensile strength which is greater than 800 MPa, a transition temperature of lower than 40 C., and an outer circumference, wherein the tube element further includes a second longitudinal portion which extends axially from the first longitudinal portion, wherein the second longitudinal portion and the first longitudinal portion form a monolithic seamless or welded tube, wherein the second longitudinal portion comprises an outer circumference which is reduced compared to the outer circumference of the first longitudinal portion, wherein the second longitudinal portion comprises a transition temperature lower than 50 C. and lower than the transition temperature of the first longitudinal portion, and wherein the second longitudinal portion is on an end of the tube element.

2. The gas pressure container as claimed in claim 1, wherein the tube element further includes at least one third longitudinal portion which extends axially from the first longitudinal portion, wherein the third longitudinal portion and the first longitudinal portion form a monolithic seamless or welded tube, and wherein the third longitudinal portion comprises an outer circumference which is reduced compared to the outer circumference of the first longitudinal portion, and a transition temperature lower than 50 C. and lower than the transition temperature of the first longitudinal portion.

3. The gas pressure container as claimed in claim 2, wherein the tube element includes two third longitudinal portions, and wherein the following correlation applies:
U.sub.12=(0.60.9)U.sub.11, and/or
U.sub.13=(0.60.9)U.sub.11, and/or
U.sub.16=(0.650.95)U.sub.11, where U.sub.11 is the outer circumference of the first longitudinal portion, U.sub.12 is the outer circumference of the second longitudinal portion, U.sub.13 is the outer circumference of one of the third longitudinal portions, and U.sub.16 is the outer circumference of another of the third longitudinal portions.

4. The gas pressure container as claimed in claim 2, wherein a wall thickness of the first longitudinal portion is less than a wall thickness of the second longitudinal portion and/or a wall thickness of the third-longitudinal portion.

5. The gas pressure container as claimed in claim 4, wherein the wall thickness of the second longitudinal portion and/or the wall thickness of the third longitudinal portion is at least 5% greater than the wall thickness in the first longitudinal portion.

6. The gas pressure container as claimed in claim 2, wherein a wall thickness of the first longitudinal portion is greater than or equal to a wall thickness of the second longitudinal portion and/or a wall thickness of the third longitudinal portion.

7. The gas pressure container as claimed in claim 2, wherein the tube element further includes a transition portion having an outer circumference that increases continuously in the direction of the first longitudinal portion, and wherein the transition portion is arranged between the second longitudinal portion and the first longitudinal portion and/or between the third longitudinal portion and the first longitudinal portion.

8. The gas pressure container as claimed in claim 7, wherein a transition region is located in the transition portion, and wherein the transition portion comprises a width which is greater than a width of the transition region.

9. The gas pressure container as claimed in claim 2, wherein the third longitudinal portion is a local predetermined breaking point arranged in a center of the gas pressure container when internal pressure is applied in the gas pressure container.

10. The gas pressure container as claimed in claim 1, wherein the end of the tube element with the second longitudinal portion is a first end of the tube element, wherein the tube element further includes a third longitudinal portion on a second end of the tube element, and wherein the first longitudinal portion is a center portion between the second and third longitudinal portions.

11. The gas pressure container as claimed in claim 1, wherein the tube element includes two first longitudinal portions between which the second longitudinal portion and/or a third longitudinal portion of the tube element extends, the third longitudinal portion having a reduced outer circumference compared to the outer circumference of the two first longitudinal portions.

12. The gas pressure container as claimed in claim 1, wherein the following applies:
deformability,.sub.12>1.05deformability,.sub.11, where deformability,.sub.11 is a plastic deformability of the first longitudinal portion in a circumferential direction of the tube element, and deformability,.sub.12 is a plastic deformability of the second longitudinal portion in the circumferential direction.

13. The gas pressure container as claimed in claim 1, wherein the first longitudinal portion and/or the second longitudinal portion comprises/comprise a metallic microstructure with a surface portion of at least 70 percent tempered martensite.

14. The gas pressure container as claimed in claim 1, wherein the following applies:
Rm,.sub.12<0.9Rm,.sub.11, where Rm,.sub.11 is the tensile strength of the first longitudinal portion, and Rm,.sub.12 is a tensile strength of the second longitudinal portion.

15. The gas pressure container as claimed in claim 1, wherein the tube element further includes a transition region having a tensile strength that continuously increases, wherein the transition region is arranged between the second longitudinal portion and the first longitudinal portion, and wherein the transition region comprises a width which is between 10 and 100 mm.

16. The gas pressure container as claimed in claim 1, wherein the second longitudinal portion of the tube element comprises a mixed ferrite-perlite microstructure with a surface portion of at least 70 percent.

17. The gas pressure container as claimed in claim 1, wherein the tube element includes a further longitudinal portion which comprises a notch in a lateral surface of the tube element, and an outer circumference with the notch being enlarged compared to the outer circumference of the first longitudinal portion.

18. The gas pressure container as claimed in claim 1, wherein the tube element further includes a transition region having a tensile strength that continuously increases, wherein the transition region is arranged between the second longitudinal portion and the first longitudinal portion, and wherein the transition region comprises a width which is between 15 and 40 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIGS. 1a to 1c show a first embodiment of the gas pressure container according to the invention;

(3) FIG. 2 shows a second embodiment of the gas pressure container according to the invention;

(4) FIG. 3 shows a third embodiment of the gas pressure container according to the invention;

(5) FIG. 4 shows a fourth embodiment of the gas pressure container according to the invention;

(6) FIG. 5 shows hardness progression on the tube element prior to reduction of the outer circumference in the second longitudinal portion;

(7) FIGS. 6a to 6c show a side view and two sectional views of the embodiment according to FIG. 4;

(8) FIGS. 7a to 7c show a side view and two sectional views of an alternative design variant with a notch; and,

(9) FIG. 8 shows a schematic side view of a gas pressure container with closure plates welded on.

(10) In the Figures, the same reference designations are used for identical or similar components, even if a repeated description is omitted for reasons of simplicity.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

(11) FIG. 1a shows a gas pressure container 1 which includes a tube element 10 having a second longitudinal portion 12 with a wall thickness WD.sub.12 and a third longitudinal portion 13 and a wall thickness WD.sub.13 at the corresponding ends E.sub.1, E.sub.2 of the tube element 10 and includes a first longitudinal portion 11 which is arranged between the second longitudinal portion 12 and third longitudinal portion 13. The second and third longitudinal portions 12, 13 comprise a smaller outer circumference U.sub.12, U.sub.13 compared to the outer circumference U.sub.11 of the first longitudinal portion 11, as can be seen in FIGS. 1b and 1c, the outer circumference U.sub.15 merging continuously in each case in a transition portion 15 from the first longitudinal portion 11 into the second or rather into the third longitudinal portion 12, 13. The first longitudinal portion 11 comprises a constant outer circumference U.sub.11. The second and third longitudinal portions 12, 13 comprise a transition temperature Tu,.sub.12, Tu,.sub.13 of lower than 50 C. which is also lower than the transition temperature Tu,.sub.11 of the first longitudinal portion 11. The first longitudinal portion 11 comprises a tensile strength of at least 800 MPa and a metallurgical microstructure with a surface portion of at least 70% tempered martensite. In the transition region 14 (shown by the broken line) between first longitudinal portion 11 and second longitudinal portion 12 or rather first longitudinal portion 11 and third longitudinal portion 13, a rather undefined mixed microstructure and/or undefined mechanical characteristic values is/are present, which is why the width B.sub.14 of the transition portion 14 is smaller than the width B.sub.12 of the second longitudinal portion 12 and B.sub.13 of the third longitudinal portion 13. In a preferred manner, the width B.sub.14 is also smaller than the width B.sub.15 of the transition region 15. FIGS. 1b and 1c show in each case a frontal view of the tube element 10. The respective outer circumferences U.sub.11, U.sub.12 and U.sub.11, U.sub.13 as well as the circumference U.sub.15 of the transition portion 15 which extends in between in each case can easily be seen. The transition temperatures T.sub.u,10, T.sub.u,11, T.sub.u,11, T.sub.u,12, T.sub.u,13, T.sub.u,15, T.sub.u,16, are named in the description, but are not shown in the figures.

(12) FIG. 2 shows a second embodiment of the gas pressure container 1 according to the invention, which includes a tube element 10 having a second longitudinal portion 12 and a third longitudinal portion 13 and a first longitudinal portion 11 which is arranged between the second longitudinal portion 12 and the third longitudinal portion 13. The second and third longitudinal portions 12,13 comprise a smaller outer circumference U.sub.12, U.sub.13 compared to the outer circumference U.sub.11 of the first longitudinal portion 11, the outer circumference U.sub.15 merging continuously in each case in a transition portion 15 from the first longitudinal portion 11 into the second and third longitudinal portions 12, 13. In longitudinal extension, the first longitudinal portion 11 comprises an outer circumference U.sub.11 which is arched slightly radially outward, the outer circumference as the outer diameter being consequently shown to be circular in this embodiment too. The second and third longitudinal portions 12,13 comprise a transition temperature Tu,.sub.12, Tu,.sub.13 of lower than 50 C. which is also lower than the transition temperature Tu,.sub.11 of the first longitudinal portion 11. The first longitudinal portion 11 comprises a tensile strength of at least 800 MPa and a metallurgical microstructure with a surface portion of at least 70% tempered martensite. In the transition region 14 (shown by the broken line) between first longitudinal portion 11 and second longitudinal portion 12 or rather first longitudinal portion 11 and third longitudinal portion 13, a rather undefined mixed microstructure and/or undefined mechanical characteristic values is/are present, which is why the width B.sub.14 of the transition portion 14 is smaller than the width B.sub.12 of the second and B.sub.13 of the third longitudinal portions 12, 13. In a preferred manner, the width B.sub.14 is also smaller than the width B.sub.15 of the transition region 15. The transition region 14 is consequently located in the transition region 15.

(13) FIG. 3 shows a third embodiment of the gas pressure container 1 according to the invention which includes a tube element 10 having a second longitudinal portion 12 at a first end E.sub.1 of the tube element 10 and a third longitudinal portion 13 at the second end E.sub.2 of the tube element 10 as well as two first longitudinal portions 11, 11 which are arranged in the region between the ends E.sub.1, E.sub.2. The second and third longitudinal portions 12,13 comprise a smaller outer circumference U.sub.12, U.sub.13 compared to the first longitudinal portions 11, 11, the outer circumference U.sub.15 merging continuously in each case in a transition portion 15 from the first longitudinal portions 11, 11 into the second or rather third longitudinal portions 12, 13. In addition, the two first longitudinal portions 11, 11 enclose a further longitudinal portion 16 which is realized in a reduced manner in the outer circumference U.sub.16 compared to the first longitudinal portions 11, 11. The outer circumferences U.sub.16, U.sub.12 and U.sub.13 can be different to one another, the dimension of the further longitudinal portion 16 being adaptable in particular to mounting parts, such as a bursting disk (not shown), which are to be joined thereto or are supported thereon inside the tube element. In contrast, the dimension of the second and third longitudinal portions 12,13 are measured such that closure plates, as shown in FIG. 7, or the like are attachable, in particular are weldable to the ends E.sub.1, E.sub.2 of the tube element 10. The second and third longitudinal portions 12,13 comprise a transition temperature Tu,12, Tu, 13 of lower than 50 C. which is also lower than the transition temperature Tu, 11, Tu, .sub.11 of the first longitudinal portions 11, 11. The first longitudinal portions 11, 11 comprise a tensile strength of at least 800 MPa and a metallurgical microstructure with a surface portion of at least 70% tempered martensite. In the transition regions 14 between first longitudinal portion 11 and second longitudinal portion 12 or rather first longitudinal portions 11, 11 and third longitudinal portion 13 as well as first longitudinal portions 11, 11 and further longitudinal portion 16, a rather undefined mixed microstructure and/or undefined mechanical characteristic values is/are present, which is why the width B.sub.14 of the transition portions 14 (shown by the broken line) is smaller than the width B.sub.12 of the second and B.sub.13 of the third longitudinal portions 12, 13. In a preferred manner, the width B.sub.14 is also smaller than the width B is of the transition portions 15. In addition, there is a wall thickness WD.sub.16 in the further longitudinal portion 16. The wall thickness WD.sub.16 can be greater or smaller than the wall thickness WD.sub.11, WD.sub.11.

(14) FIG. 4 shows a fourth embodiment of the gas pressure container 1 according to the invention which includes a tube element 10 having a further longitudinal portion 16 with a smaller outer circumference U.sub.16 compared to the two first longitudinal portions 11, 11, which extend axially therefrom to the ends E.sub.1, E.sub.2 of the tube element 10 and have an outer circumference U.sub.11, U.sub.11.

(15) The outer circumference U.sub.16 is adapted in particular to mounting parts, such as a bursting ring, which are to be joined thereto inside the tube element or are supported thereon. At the ends E.sub.1 and E.sub.2 of the tube element 10 are a second and a third longitudinal portion 12, 13 which, with reference to the longitudinal direction, are very short and which have the outer circumferences U.sub.12, U.sub.13 which are smaller than the non-reduced outer circumference of the first longitudinal portions U.sub.11, U.sub.11 but greater than the reduced outer circumference U.sub.16 of the further longitudinal portion 16 in a central longitudinal portion. The second and third longitudinal portions 12,13 comprise a transition temperature Tu,12, Tu,13 of lower than 50 C. which is also lower than the transition temperature Tu,11 of the first longitudinal portion 11, 11 . The first longitudinal portion 11, 11 comprises a tensile strength of at least 800 MPa and a metallurgical microstructure with a surface portion of at least 70% tempered martensite. In the transition region 14 between first and further longitudinal portions 11, 11, 16, a rather undefined mixed microstructure and/or undefined mechanical characteristic values is/are present. FIG. 5 shows the hardness progression on a tube element 10 according to the invention prior to reduction of the outer circumference, proceeding from the first end E1 in the axial direction via a second longitudinal portion 12 to the first longitudinal portion 11. It is possible to see the lower hardness and consequently tensile strength in the second longitudinal portion and a transition region 14 with increasing hardness values up to a maximum which then remain constant in the first longitudinal portion 11.

(16) FIGS. 6a to 6c once again show a design variant according to FIG. 4. FIG. 6b shows a cutting line b-b from FIG. 6a. The constant circular outer circumference U.sub.11 of the first longitudinal portion 11 can be seen. FIG. 6c shows a cutting line c-c from FIG. 6a through the further longitudinal portion 16. It can be seen that this too comprises a circular outer circumference U.sub.16 which is, however, smaller than the outer circumference U.sub.11 of the first longitudinal portion 11 which is located behind it in the viewing direction according to FIG. 6c.

(17) FIGS. 7a to 7c show an alternative design variant to this. According to FIG. 7b, which shows a sectional representation b-b from FIG. 7a, a constant outer circumference U.sub.11 of the first longitudinal portion 11 is shown once again. In a central region with reference to the longitudinal direction, this latter comprises a notch 19 or rather cavity. The outer circumference U.sub.19 produced by the notch 19 is enlarged compared to the outer circumference U.sub.11 which is located behind it in the viewing direction according to FIG. 7c. The notch 19 can be introduced into the lateral surface of the tube element 10 in any arbitrary geometric form. In particular, the further longitudinal portion produced with the notch 19 can be applied to any arbitrary exemplary embodiment in said publication.

(18) FIG. 8 shows a schematic view of the tube element 10 with closure plates 17. The closure plates 17 are seal welded to the tube element by way of a circumferential weld seam 18. The closure plates can be welded to the ends E1 and E2 on all previously described exemplary embodiments.

(19) The foregoing description of some embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The specifically described embodiments explain the principles and practical applications to enable one ordinarily skilled in the art to utilize various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. Further, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as described by the appended claims.