Patent Application
20050156419
The invention relates to a device for actuating a vehicle safety system, in particular an inflation device for a gas bag.
Such a device is known from DE 196 26 463 A1. The gas generator has a metal band looped around its outside, which is deformed plastically by the gas flow and exposes flow paths for the gas in the direction towards the gas bag. The flow direction of the gas emerging from the gas generator is influenced by the metal sheet, in particular a direct flow of gas against the gas bag wall is avoided.
It is an object of the invention to influence the outflow behavior of the gas dependent on temperature.
A device for actuating a vehicle safety system comprises a gas generator having an outer housing and a rigid gas deflection part provided outside the outer housing. The device further includes at least one elastic fastening means for the gas deflection part, which presses the gas deflection part, when the gas generator is not actuated, against said gas generator and upon outflow of gas varies the distance of the gas deflection part from the outer housing depending on the gas pressure.
In the device proposed, the operation is not carried out with the pure plastic deformation of the gas deflection part; rather, an elastic fastening means is provided, by which different distances of the gas deflection part from the outer housing are obtained through the gas pressure, which continues to be elastic even after the maximum stress has been applied onto it, and brings about a returning of the gas deflection part. If, for example, the gas pressure becomes less at the end of the outflow process, then the elastic fastening means again reduces the distance between the outer housing and the gas deflection part, so that the outflow opening arising between these two parts becomes smaller again. The curve of the gas pressure (known as the outflow behavior) is, as is known, dependent on temperature. Through the elastic fastening means, the counter-pressure applied by the gas deflection part is varied, so that the burning rate of the pyrotechnic charge contained in the gas generator changes.
An advantage of the elastic fastening means also consists in that it has various elastic constants as a function of the temperature. At low temperatures it is harder, which is desirable with regard to the output characteristic, because it exposes the outflow openings in the outer housing of the gas generator at a later point in time. At higher temperatures the elastic fastening means is softer and exposes the openings more quickly.
The gas deflection part is preferably a baffle plate which is constructed for example in a trough shape and lies against the covering surface of the usually cylindrical gas generator.
When the gas generator is not actuated, an embodiment makes provision that the gas deflection part is pressed against the outer housing and, for example, closes the outflow openings in the outer housing. Theoretically it would, of course, also be possible to keep the gas deflection part a gap away from the outflow openings when the gas generator is not actuated.
The fastening means is preferably made of elastomeric material, for example in the form of one or more bands or tubes. The fastening means can, of course, be fastened on any parts of the device, but it is preferably fastened on the gas generator, so that the gas deflection part and the fastening means together with the gas generator form a self-contained pre-assembled unit.
In order to simplify the arresting of the fastening means on the gas deflection part and/or on the gas generator, it is guided around the deflection part or around the gas generator according to one embodiment. In the preferred embodiment it is guided around both, by the fastening means being constructed as a closed, ring-shaped body, which also improves its stability.
Another embodiment of the invention makes provision that, instead of the rigid gas deflection part defining a separate part, it is an integral portion of the elastic fastening means. In this case, the gas deflection part has a heat-resistant coating applied on an inner side directed towards the gas generator. Thereby, the gas deflection part is no longer rigid; it rather is elastic. In this embodiment, one component can be saved.
In
Reference 20 designates two igniter units in which a pyrotechnic material is contained. The gas generated in the igniter units 20 flows into the interior of the outer housing 14, in order to mix there either with cold gas which is housed in a pressure chamber, or to ignite a further pyrotechnic charge inside the outer housing 14.
When gas leaves the outer housing 14 via the outflow openings 22, it flows against the baffle plate 16 and pushes the latter contrary to the force of the fastening means 18 away from the outer housing 14 (see
At lower temperatures (operating range up to −40 degrees C. to +85 degrees C.) the elastomer of the fastening means 18 is harder, so that the outflow openings 22 are kept closed for a longer period and a higher gas pressure can build up in the outer housing 14 first.
The outflowing gas flows, as stated, firstly against the baffle plate 16 and can only subsequently flow against the outer wall of the gas bag 10, so that entrained particles have cooled down until they strike onto the gas bag wall.
In the embodiment illustrated in
In the embodiment according to
On activation of the gas bag, there will arise only axial outflow slits from the device, because the fastening means 18 acts like a channel wall between baffle plate 16 and outer housing 14.
In both embodiments the baffle plate 16 is arrested against displacement for example by gluing, clamping or flanging on the fastening means 18.
Instead of the baffle plate 16 shown in
Alternatively, an insulation such as a thin foil could be provided on the outer side of the outer housing 14 at least in the region of the outflow openings 22, e.g. could be glued on. This insulation is designated by reference numbers 32, 34 in
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2004 000 801.7 | Jan 2004 | DE | national |
