GAS GENERATOR

Abstract

The present invention relates to a gas generator, comprising a comprising a tubular element (10) with high low-temperature toughness. The gas generator is characterized in that the tubular element (10) has a ductile fracture behavior at temperature to at least 196 C., the tubular element (10) has a minimal tensile strength of 650 MPa, the tubular element (10) has a cubic face-centered austenitic structure with at least 90 area percentage and the tubular element (10) consists of a steel alloy which has a manganese content of at least 14.0 wt %

Claims

1. Gas generator, comprising a tubular element (10) with high low-temperature toughness, characterized in that the tubular element (10) has a ductile fracture behavior at a temperature to at least 196 C., the tubular element (10) has a minimal tensile strength of 650 MPa, the tubular element (10) has a cubic face-centered austenitic structure with at least 90 area percent and the tubular element (10) consists of a steel alloy which has a manganese content of at least 14.0 wt %.

2. Gas generator according to claim 1, characterized in that the tubular element (10) consists of a steel alloy which has a manganese content of at least 17.0 wt %.

3. Gas generator according to claim 1, characterized in that the steel alloy, of which at least the tubular element (10) of the gas generator consists, comprises besides iron and impurities resulting from smelting, the following alloying elements, indicated in wt %: C>0.03 Mn>14.0 Al>0.03

4. Gas generator according to claim 3, characterized in that the carbon content of the steel alloy is in the range of 0.3-0.7 wt %.

5. Gas generator according to claim 3, characterized in that the aluminum content of the steel alloy is more than 1.0 wt %.

6. Gas generator according to claim 1, characterized in that the steel alloy of which at least the tubular element of the gas generator consists, consists, besides iron and of impurities resulting from smelting, of the following alloying elements indicated in weight percent: C 0.1-1% Si<2.5% Mn14% Al>1% B<0.005% Ni<2.00% Cu<2.00% Nb<0.30 Ti<0.30% V<0.30% N<0.60% P<0.01% and S<0.01%

7. Gas generator according to claim 1, characterized in that the minimal tensile strength of the tubular element (10) is at least 1100 MPa.

8. Gas generator according to claim 1, characterized in that the tubular element (10) has a ductile fracture behavior after cold forming of the tubular element (10) by at least 2%, in particular at least 10%.

9. Gas generator according to claim 8, characterized in that the cold forming is a modification of the outer diameter of the tubular element (10).

10. Gas generator according to claim 1, characterized in that the tubular element (10) has ductile fracture behavior at a temperature to at least 200 C.

11. Gas generator according to claim 1, characterized in that the gas generator (1) is a gas generator for a vehicle occupants protection device or a passenger protection device, in particular an airbag.

12. Gas generator according to claim 1, characterized in that the gas generator (1) is a gas generator for a fire extinguisher for airplane engines, for an actuator of an ejection seat or for position controls for spacecrafts.

13. Gas generator according to claim 1, characterized in that the tubular element (10) is a seamless pipe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 shows a schematic depiction of the construction of an embodiment of the gas generator according to the invention; and

[0045] FIG. 2: shows a schematic depiction of the construction of a further embodiment of the gas generator according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0046] In the embodiment shown in FIG. 1 the gas generator 1 comprises a tubular element 10, which is closed at one end. In the area of this end, the tubular element 10 is covered by a membrane 11. At the opposite end of the tubular element 10 a diffusor 13 adjoins. In the diffusor 13 gas outlet openings (not shown) are provided. By means of an igniter 12 which is arranged in the tubular element 10, the gas which is stored in the tubular element under pressure can be expanded. Thereby, the membrane 11 is destroyed and the gas streams into the diffusor 13 and from there is released via the gas outlet openings. The gas is for example let into an inflatable part of an airbag (not shown).

[0047] In FIG. 2 a further embodiment of the gas generator 1 according to the invention is shown. Also this gas generator 1 comprises a tubular element 10. In the embodiment shown in FIG. 2, the tubular ends are tapered or drawn in. The tapering of the tubular ends may be generated by cold forming. In the depicted embodiment, the tubular ends each have a diameter D.sub.1, which is smaller than the diameter of the tubular element 10 in its middle section. Also in the embodiment shown in FIG. 2, the gas generator has a combustion chamber 14, wherein an ignitor as well as the further pyrotechnical components is provided. At the tubular end the combustion chamber 14 is closed by a plate 17 which is welded thereto. Cold gas storage 15 adjoins to the combustion chamber 14. This is separated from the combustion chamber 14 by the membrane 11, which can also be referred to as bursting plate. The cold gas storage 15 lies in the area of the tubular element 10, which has the larger diameter D.sub.0. The diffusor 13 adjoins to the cold gas storage 15. In FIG. 2 in the area of the diffusor 13 a filling hole 16 is shown. The tubular end of the diffusor 13 is welded with a plate 17, that is it is closed thereby.

[0048] In the cold gas storage 15 for example a pressure of 580 bar may be present. In the combustion chamber 14, the pressure may increase for example from 580 bar to 1,200 bar when igniting the ignitor. The gas generator 1 according to the invention can reliably withstand this pressure due to its properties.

[0049] With the present invention, the tubular element in the usage for airbags, the said fire extinguisher or ejection seats and position control for spacecrafts, is subjected to inner pressure load and potentially to dynamic bursting load. With the inventive gas generator herein a sufficient safety is given due to the low-temperature toughness and strength.

[0050] With the gas generator according to the invention and in particular with the manganese steel which is used at least for the tubular element, a high strength can be achieved and the overall weight can be decreased. Furthermore, the gas generator according to the invention provides high reliability even in extreme situations due to the good low-temperature toughness. In particular, a brittle or ductile failure is not does not have to be feared when using the gas generator.

[0051] The present invention has a number of advantages. In particular, a brittle failure at low temperatures does not have to be feared. Nevertheless, a high strength, in particular a strength of 700 MPa to 1400 MPa, preferably 1000 MPa or 1100 MPa is achieved. In spite of the high strength the steel alloy which is used for the manufacture of at least the tubular element, has a good formability. In particular, the tubular element can also be attached to the gas generator by cold forming without making the formability more difficult. Finally, the weight of the gas generator can be reduced. Thereby, requirements for lightweight construction can be achieved with a gas generator. By reducing the material consumption for the gas generator, also the higher price of the alloy to be used which is to be expected due to the addition of manganese can be reduced.

LIST OF REFERENCE NUMBERS

[0052] 1 gas generator [0053] 10 tubular element [0054] 11 membrane [0055] 12 ignitor [0056] 13 diffusor [0057] 14 combustion chamber [0058] 15 cold gas storage [0059] 16 filling hole [0060] 17 plate