Gas generating system

Abstract

The present invention generally relates to gas generant compositions for inflators of occupant restraint systems, for example. A gas generating composition 12 formed in accordance with the present invention includes an alkyl cellulosic fuel / binder, an oxidizer, and a burn inhibitor or ignition catalyst. A vehicle occupant protection system 180, and other gas generating systems, incorporate the compositions of the present invention.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims the benefit of U.S. Provisional Application Ser. No. 60 / 666,964 having a filing date of Mar. 31, 2005.TECHNICAL FIELD [0002] The present invention relates generally to gas generating systems, and to gas generant compositions employed in gas generator devices for automotive restraint systems, for example. BACKGROUND OF THE INVENTION [0003] The present invention relates to nontoxic gas generating compositions that upon combustion rapidly generate gases that are useful for inflating occupant safety restraints in motor vehicles and specifically, the invention relates to thermally stable nonazide gas generants having not only acceptable burn rates, but that also, upon combustion, exhibit a relatively high gas volume to solid particulate ratio at acceptable flame temperatures. [0004] The evolution from azide-based gas generants to nonazide gas generants is well-documented in the prior art. The advantages of nona...

AI Technical Summary

Benefits of technology

[0011] Typical micro gas generators use nitrocellulose or smokeless powder compositions for gas generation in a device. These compositions often result in relatively higher amounts of carbon monoxide. Furthermore, ballistic tailoring is not readily accomplished with the use of nitrocellulose. These are non-nitrocellulose compositions containing an oxidizer, a fuel, and a binder. Performance characteristics (i.e. ballistic output) related to burning rate can be varied based on the particle size distribution of the oxidizer component. In general, as the particle size distribution of the oxidizer is reduced, the burning rate of the propellant composition increases thereby enhancing the ballistic properties. As the particle size increases, the burning rate decreases and thus the ballistic output is reduced. Accordingly, the ballistic properties may be tailored in this manner. Average particle size ranges from 10 to 150 microns. Combinations of particle size distributions within said range can also be considered for the purpose of modifying performance. Ballistic tailoring can also be achieved by varying the shape, size and surface treatment, or any combination thereof of the propellant grains. Various propellant processes and techniques affecting propellant grain density, porosity, and surface finish (i.e. high or low exposed burning surface area) can also be employed to tailor ballistic output, for instance to achieve a regressive burn profile. A discreet propellant geometry such as a small cylinder, processed in a particular way such as extrusion, exhibits a porous center and also exhibits a regressive type burn profile. Limiting damage to equipment incorporating gas generants, seatbelt pretensioners for example, is thereby facilitated.

[0012] In sum, the present invention includes gas generant compositions that optimize the production of gas combustion products and minimize solid combustion products while retaining other design requirements such as reduced hygroscopicity and thermal stability. These and other advantages will be apparent upon a review of the detailed description.

Problems solved by technology

These compositions often result in relatively higher amounts of carbon monoxide.

Furthermore, ballistic tailoring is not readily accomplished with the use of nitrocellulose.

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