DE9010853U1 - Gas generator - Google Patents

Description

,ie.07.1990, 2533A

Pfister/Th 10933

Gas generator

The innovation relates to a cylindrical gas generator for inflating the gas bag of an impact protection device, according to the generic term of claim 1.

Such a gas generator is known from DE-Hi 38 34 892, where the special feature of _the flow guide body, also called flow deflection and flow divider body, is ". The flow guide body should be

* this design provides a uniform Sasverti>i* ^ä "ng and thus a homogeneous

rod ' ?aufschilling ^with the advantage of efficient filter use. Since the gases produced are led directly from the gas generation chamber to the filter without major diversions, there is a high probability that the majority of the hot slag particles contained in the gas flow will enter the filter and impair its fluid mechanics properties, and that slag particles will penetrate through the filter to the outside. This filter contamination or loading, which must be taken into account in advance, requires a relatively bulky, heavy and expensive filter insert.

With regard to the flow guide body designs, it should be noted that the Christmas tree-like versions are relatively thick-walled and difficult to manufacture for mechanical reasons, e.g. as turned or cast parts.

The pot-shaped and stepped version shown in the lower half section in Fig. 3 of DE-PS 38 34 892 is more favorable, and can be produced relatively thin-walled and inexpensively, e.g. as a deep-drawn sheet metal part. The disadvantage here is that the interior of the pot-shaped body remains unused in terms of flow and feeding technology.

In contrast, the task of the innovation is to create a gas generator which, through structural and fluidic measures,

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a better pre-separation of the slag particles and thus a relief of the outlet-side filter insert with the result _that a simpler, more efficient and less expensive* design of the same and of the gas generator as a whole is possible.

This object is achieved by the features characterized in claim 1.

Based on a version known from the state of the art described above, the flow guide body is designed as a thin-walled, pot-shaped component with a diameter that gradually tapers from the open end to the bottom. The flow guide body is arranged with its open end facing the gas generation chamber and is sealed in this area towards the filter insert. In the bottom area it is provided with one or more passage openings for the gas generated. In this way, the gas first flows through the interior of the flow guide body, passes through its bottom, is deflected by approx. 180° in the area of the filter chamber front wall and then distributed from the outside of the flow guide body to the filter surface. This type of flow guidance is significantly more effective in terms of slag pre-separation than the known types. It is possible to provide additional fittings for flow redirection and/or gas filtration inside the flow guide body if required.

Claims 2 to 5 contain preferred embodiments of the gas generator according to claim 1.

The innovation is then explained in more detail using the drawings. In a simplified representation,

Fig. 1 shows a partial longitudinal section through a gas generator in the area of the filter chamber, with an additional filter element inside the flow body shown below the center line,

• S &igr;'".'" ^: ■ 1-8.07.1990, ,2533A

PfUter/Th

10933

Fig. 2 shows a comparable longitudinal section of two variants with internals for flow deflection and pre-filtration, where one variant is shown above the center line and the other below the center line.

The cylindrical gas generator 1 comprises a gas generation chamber 2 with an igniter and a propellant charge (both not shown) and at least one filter chamber 5. The gas generation chamber housing 3 and the filter chamber housing 6 merge directly into one another and are firmly connected to one another, for example by electron beam welding, gluing or screwing. An end wall 4 delimits the gas generation chamber 2 in the axial direction, with passage openings 15 allowing the generated gases to flow into the filter chamber 5. The filter chamber housing 6 is delimited at its free end (on the right in Fig. 1) by the closed end wall 7. On the circumference it has several outlet openings 9, for example in the form of elongated holes, which open into an inflated gas bag (not shown). From the inside of the housing, a tubular filter insert 8 is located in front of the outlet openings.

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5 is achieved by a pot-shaped flow guide body 10, which has multiple diameter steps over its axial length. Its open end 11 faces the front wall 4 of the gas generation chamber 2, its base 13 faces the outer front wall 7 - at an axial distance. The edge 12 of the flow guide body 10, which forms the open end 11, is fitted into the filter chamber housing 6 as tightly as possible in order to prevent a short-circuit flow from the passage openings 15 past the edge 12 to the filter insert 8. As the arrows in the upper half of Fig. 1 indicate, the gas coming from the passage openings 15 first flows through the tapered interior of the flow guide body 10, which in this way acts as a pre-separation space for slag particles contained in the gas. The multi-stepped contour of the flow guide body 10 supports the separation effect through local flow deflection and turbulence. The gas passes through the passage openings 16 with relatively strong deflection in the area of the base 13 and the

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Pfister/Th 10933

Front wall 7 on the outside of the current 1 ed body 10 and is from f

there evenly on dip radially inner surface of the filter insert 8 f

The support plate 14 arranged in the area of the front wall 7 improves the flow guidance in the area of the base 13, fixes the flow guide body 10 axially and supports the filter insert 8 radially from the inside against the filter chamber housing ö, which prevents short-circuit flows at the filter insert 8 ναι when flowing out into the open. In a similar way, the filter insert ^; i is supported radially at its left end by the step of the flow guide body 10 adjacent to the edge 12.

If support of the filter insert 8 in the area of the front wall 7 is not required, the support plate 14 can be omitted, the base 13 can lie directly against the front wall 7, in which case, instead of the axial passage opening 16 in the base 13, radial passage openings would have to be provided in the cylindrical part of the flow guide body 10 adjacent to the base 13.

In the design shown in Fig. 1 below the center line, a filter element 24, e.g. in the form of a mesh, is additionally present in the condensate separator body, which further improves the particle pre-separation and exerts an additional cooling effect on the gases. At this point, it should be remembered that the innovation aims to relieve the strain on the filter insert on the outlet side and thus make it smaller, lighter and cheaper.

Fig. 2 shows examples of further possibilities for improving the pre-separation inside the flow guide body. The a flow-deflecting plates are combined with filter elements. |

The version shown above the center line sees a sheet 21 with i

a central passage opening 17 in the form of a tubular channel es %

and with several eccentric openings 18. In the %

the walls of the sheet 21 and from the adjacent cylindrical section

area of the flow guide body is a filter element 25 7

5 : ' 1^.07.1990, 2533A " ' >fister/Th 10933

through which part of the gas is guided without major flow diversion. The other part of the gas flow is diverted towards the center and bypasses the filter element 25 through the passage opening 17. This provides a combination of the "flow diversion" and "filtration" measures.

The version below the center line works with two plates 22 and 23 and with a filter element 26. The first plate 22 is arranged close to the gas outlet from the gas generation chamber and causes a strong flow deflection towards the center. For this purpose it only has one central passage opening 19. The second plate 23 is located downstream of the first and only has off-center passage openings 20, which causes a flow deflection from the center to the outside. The space between the plate 23 and the bottom of the flow guide body is filled with a filter element 26 through which the entire gas flow is guided.

It is understood that the measures "flow deflection", "flow division" and "filtration" can be implemented in combination with other arrangements without departing from the scope of the innovation.

Furthermore, it is self-evident that the gas generator according to the innovation can also be designed symmetrically, i.e. that a filter chamber with a flow guide body can be arranged axially on both sides of the gas generation chamber.

Claims (5)

V8.07.1990, 2533m Pfister/Th 10933 Gas generator protection claims 1. Cylindrical gas generator for inflating the gas bag of an impact protection device for one or more occupants of a vehicle, in particular for the front passenger or passengers of a motor vehicle, consisting essentially of a gas generation chamber with igniter and propellant charge and of at least one filter chamber connected axially thereto with circumferential outlet openings, with a tubular filter insert arranged fluidically upstream of the outlet openings and with a flow guide body which is at least ^largely rotationally symmetrical, has multiple diameters and is arranged centrally in the filter chamber, characterized in that the flow guide body (10) is designed as a thin-walled, pot-shaped component with a diameter which tapers step by step from the open end (11) to the base (13), that the flow guide body (10) is directed with its open end (ii) towards the gas generation chamber (2), with its base (13) towards the outer front wall (7) is arranged towards the filter chamber (5), that at least in the bottom (13) or in the bottom region of the flow guide body (10) there is at least one passage opening (16) for the gas produced, that the edge \1 surrounding the open end (11) of the flow guide body (10) is at least largely sealed towards the filter insert (8), and that in the interior of the flow guide body (10) further installations for flow diversion (metal sheets 21, 22, 23) and/or for gas filtration (filter elements 24, 25, 26) are provided if necessary. 2. Gas generator according to claim 1, characterized in that the flow guide body (10) is designed as a deep-drawn sheet metal part. '·: * 2 1 ' - ^: ^3.07.199O, 2533A Pfister/Th 10933 3. Gas generator according to claim 1 or 2, characterized in that the gas generation chamber-side end of the tubular filter insert (8) is supported radially from the inside by the flow guide body (10) and is axially fixed, and that the axially opposite end of the filter insert (8) is supported radially from the inside by an additional support plate (14). 4. Gas generator according to one or more of claims 1 to 3, characterized in that one or more plates (21, 22, 23) running essentially transversely to its axis and resting against its circumferential steps with one central (17, 19) and/or with several eccentric passage openings (18, 20) for the gases generated are arranged in the interior of the flow guide body (10). 5. Gas generator according to one or more of claims 1 to 4, characterized in that one or more filter elements (24, 25, 26), preferably in the form of a knitted mesh, are arranged in the interior of the flow guide body (10).