Investigation on dual stage pyrotechnic gas generator used to stage the inflation of an airbag in a vehicle occupant restraint system was studied. Different types of the two combustion chamber partitions of the inflator were proposed. A simulated model is developed to fit the tested data and the results were in good agreement. Major factors i.e. gas generant loads, delay time, partition volume etc. affecting the pressure-time curves were used to simulate the performances of a dual stage inflator made with stainless steel material. Dual stage pyrotechnic inflators were made through the use of two combustion chambers in either isolation or the second combustion chamber being within the first combustion chamber. Deployment modes may involve deployment of both stages at once or the first followed by the secondary at some later time to provide the desired gas delivery event. The investigation of a two-stage module containing two squibs and boosters showed a broad variety of pressure-time curves achievable by time delayed initiation. An improved dual stage pyrotechnic inflator was accomplished. The inflator housing defines a first chamber containing a quantity of a first gas generant material ignitable to produce first combustion products, the second combustion chamber is within the first combustion chamber. The second chamber includes a novel exit orifice adapted to place the second combustion products in fluid communication directly to the common exit vents. In recent commercial dual stage inflators, the second combustion products are in contact with the contents of the first combustion chamber. The present improved dual stage inflator is designed to eliminate any vent holes in the periphery of the second chamber, it is possible to avoid autoignition of the pyrotechnic materials within the second chamber upon thermal contact by the combustion products formed upon ignition of the pyrotechnic materials in the first chamber. Comparisons with others will be commented on. For the covering abstract see ITRD E126782.
Samenvatting