Gas generator unit

Described is a gas generator unit comprising of a cylindrical gas generator (10), the lateral surface (10a) of which demonstrates emission holes (12) arranged in a thrust-neutral manner within a ring-shaped area (10b), and a deflector element (20), which is rigidly connected to the gas generator (10) and is made of a heat resistant material and at least surrounds the ring-shaped area (10b) at least partially. To make the gas generator harmless in the event of a fire, the deflector element (20) demonstrates, in an inflow area (20a) opposite the ring-shaped area (10b), borings (22), which are sealed by at least one blocking element (24, 32) made of a meltable or combustible material, the borings being arranged in such a manner that the gas generator unit is thrust-neutral in the absence of the blocking element (24).

FIELD OF THE INVENTION

The invention relates to a gas generator unit for an automotive airbag restraint system.

BACKGROUND OF THE INVENTION

Cylindrical gas generators, whose metal surfaces have discharge or emission holes arranged in a thrust-neutral manner within a ring-shaped area, are known for filling airbags. To this end, the ring-shaped area can be relatively small, or can extend over nearly the entire length of the lateral surface. Such an arrangement of emission holes has the advantage that, in case of an unintentional triggering of the gas generators, such as in a warehouse fire, the escaping gas will not accelerate the gas generators like a rocket.

In many applications, it is nevertheless necessary to completely or partially deflect the gas flow issuing from such a gas generator. It is known from WO 02/079008 A1, for example, to arrange a deflector element with a semicircular cross section on the lateral surface of such a gas generator, the deflector element covering half of the emission holes. This serves to protect the surrounding airbag fabric and causes the flow direction of the escaping gas to be oriented radially relative to the longitudinal axis of the gas generator.

DE 20 2004 009 002.3 discloses, among other things, a gas generator unit in which a bushing, which surrounds the cylindrical gas generator and forms a deflector element, deflects the gas flow axially.

The gas generator units, which consist of a gas generator and a deflector element rigidly connected to the gas generator, are frequently prefabricated as a subassembly and possibly placed in intermediate storage. However, these have the disadvantage that there is no thrust-neutrality and the gas generator units represent considerable danger in the event of a warehouse fire.

SUMMARY OF THE INVENTION

It is therefore the objective of the invention to develop a gas generator unit to the effect that it is thrust neutral and harmless in the event of a warehouse fire and won't fly around when gas is expelled from the discharge holes.

The deflector element of the gas generator unit according to the present invention features borings, each of which are sealed by a blocking element made of a meltable or combustible material, located in the inflow area, i.e. the area located opposite the emission holes. To this end, a single blocking element can be provided for all borings or a separate blocking element can be provided for each boring. The thickness and material of these blocking elements are chosen in such a manner that they can withstand the gas escaping from the gas generator for the short time while the gas is escaping under a situation of deploying an associated airbag, but that they will lose their mechanical stability by burning or melting upon further thermal action, substantially more than 100 degrees over several minutes for example. The deflector element itself consists of a heat-resistant material, preferably metal.

Advantageous embodiments of the invention arise from the dependent claims and from the example embodiments, which will now be presented in more detail in reference to the drawing. The drawing shows:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 to 3depict a first example embodiment of the present invention. The gas generator unit comprises a cylindrical gas generator10and a deflector element20. The gas generator discharge or emission holes12are located within a ring-shaped area10bof the lateral surface10aof the gas generator10. The deflector element20extends over the entire length of the gas generator10and has a semicircular cross section. The deflector element20fits into a rear section10cof the lateral surface10aof the gas generator10.

The inflow area20aof the deflector element20is located opposite the ring-shaped area10bwithin which the emission holes12are located. The gas flow issuing from the gas generator strikes this inflow area20adirectly. Holes or borings22are arranged in this inflow area20a. These borings22are relatively large-area and are connected to one another only by relatively thin webs. A blocking element24, which consists of plastic, is provided in each of these borings22. The blocking elements24can be formed by injecting plastic into the borings22. To this end, the blocking elements24engage the edge of the borings22to some extent, so that a positive connection results (only represented schematically inFIG. 3). The material and thickness of the blocking elements24must be chosen as a function of the geometry and of the gas generator output in such a manner that the blocking elements remain mechanically stable over the activation period of the gas generator. The material is furthermore chosen in such a manner that it loses its mechanical strength or burns if it is exposed to the heat, over 200° C. for example, for a relatively longer time, i.e. as a rule over several minutes. For this case, a “relatively longer time” is meant to define a time period longer than the activation period of gas generator10. Many plastics meet these requirements. The deflector element20preferably consists of steel sheet.

If the gas generator20is actuated, the gas generator unit behaves as depicted inFIG. 1, i.e. the gas is deflected in such a manner that it flows off in a direction directed radially from the gas generator unit. In the event of a fire, however, the borings become open as the blocking elements or method of burn away and therefore the gas flows in all radial directions so that the gas generator unit behaves in a thrust-neutral manner.

FIGS. 4 and 5depict a gas generator unit as it can be used in an arrangement as shown inFIG. 7.

In this case, the bushing26, which preferably consists of metal, forms the deflector element. In the vicinity of the annular gap30, which is located between the ring-shaped area10bof the lateral surface10aand the bushing26, the bushing demonstrates borings22located essentially opposite the gas discharge holes12. These borings are covered by the plastic ring32, which is inserted into the bushing26and forms the blocking element in this case. The material and thickness of this plastic ring32are chosen in such a manner that it maintains its stability for the time that the gas generator operates during a normal deployment. If a warehouse fire should nevertheless occur, then the plastic ring32melts and opens the borings22, so that a large portion of the gases issuing from the gas discharge holes12escapes through these symmetrically arranged borings22, the gas generator unit thereby behaving in an essentially thrust-neutral manner.

The deflector element20is rigidly connected to the gas generator in both example embodiments. In both cases, this is achieved, among other things, in that the deflector element rests on the lateral surface of the gas generator in sections. As a rule, other connecting means, which however are not illustrated here, are provided.

The deflector element20preferably consists of metal in both embodiments. Other materials are possible, however, assuming that they are essentially more heat-resistant than the blocking elements.