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Variable Outputsolid Propellant Inflator

IP.com Disclosure Number: IPCOM000032345D
Publication Date: 2004-Nov-02
Document File: 2 page(s) / 33K

Publishing Venue

The IP.com Prior Art Database

Abstract

Dual stage inflators with output ratios between 50:50 and 80:20 for the first and second stage are used to match the inflation energy delivered to airbags more closely to the required energy for restraints function.

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Solid Extruded Propellant Variable Output inflator

Background

Dual stage inflators with output ratios between 50:50 and 80:20 for the first and second stage are used to match the inflation energy delivered to airbags more closely to the required energy for restraints function.

 Early single stage

                                                                                                                                                                                                        Second stage

 % Energy more than required

                                                                                 for lower speed crash

           Energy

                                                                                                                                                                                                        First stage

Energy required to restrain occupant

                                                                      Crash velocity

Inflators are being developed with variable output to better tailor the inflator output energy to the required restraint level.  It is clear that the more stages are added the closer tailoring can be achieved, however the relative improvement is reduced and the benefit of infinitely variable output over say 3 or 4 stages is questionable.  This is particularly true until sensoring systems become more capable of determining the exact restraint force required according to occupant and crash considerations.

Inflators from Autoliv use a solid extruded propellant where the burn rate is controlled by the surface area to volume rate of the extruded propellant.  To form the extrusion a binder is used with the fuel.  Current designs use a high temperature fuel to ensure the binder is consumed in the combustion process so that the requirements for the inflator filter are reduced.  (However the gases cooling in the atmosphere of the bag will produce gas + solids like salts)

Description of Invention

Concept is to use the tailor ability of combustion rate according to surface area and extrude a section with different surface area to volume zones and ignite these zones at different times according to the required output curve.  Ignition could be by multiple ig...