TWO CHAMBER GAS GENERATOR

Abstract: A gas generator (10) utilizes a housing (12) having two combustion chambers (22, 24) defined by a partition (20) disposed intermediate the ends of the housing (12) and retained by a pair of crimps (60 and 62, respectively) disposed on opposite sides of the partition (20).

Description: TWO CHAMBER GAS GENERATOR CROSS-REFERENCE TO RELATED APPLICATION This application is based on provisional application Serial No. 60/1 21 ,91 2 filed on February 26, 1 999. BACKGROUND OF THE INVENTION The present invention relates to gas generators used to inflate air bags in an automobile occupant protection system and, more particularly, to an improved dual chamber gas generator wherein structural integrity of each chamber is assured by a novel dual crimp. Inflation systems for deploying an air bag in a motor vehicle generally employ a single gas generator in fluid communication with an uninflated air bag. The gas generator is typically triggered by a firing circuit when the sensed vehicle acceleration exceeds a predetermined threshold value, as through the use of an acceleration-responsive inertial switch. However, air bag inflation systems utilizing a single gas generator suffer from the disadvantage that the onset pressurization/inflation rate is generally set to provide aggressive initial inflation in order to achieve a particular inflation time related to occupant position. An aggressive onset rate of pressurization becomes problematic in situations where the occupant is out of position. More specifically, rapid onset pressurization of the air bag can cause the air bag to impact against the occupant with enough force to injure the occupant. The airbag volume and inflating capacity are designed to protect both large and small occupants and are generally not variable within the single gas generator. Occasionally, when an air bag utilizing a single gas generator is deployed, smaller occupants, usually children and smaller women, have been seriously injured. Commonly owned U.S. Patent No. 5,400,487 discloses an inflation system which overcomes the above problem by utilizing a plurality of gas generators which are controllably ignited to provide a variable inflation profile which can be tailored to any given occupant weight and/or position and for any crash type. While this arrangement dramatically improves the inflation system's ability to protect an occupant, it does so at significant expense and complexity. The multiple gas generators and squibs add considerable cost to the system, while the firing control circuitry requires sophisticated processors capable of accurately timing the various ignition profiles. Another proposal, as taught in commonly owned Patent No. 5,934,705, is a gas generator having two chambers in a single housing defined by a mechanically retained wall between the ends thereof. Each housing is of a predetermined size that is determinative of the propellant capacity and consequently, of the inflating capability of each chamber. Upon the occurrence of a vehicle collision, depending on the weight of the passenger, either chamber or both may be selectively ignited thereby inflating the protective airbag. However, the structural integrity of such a known dual chamber inflator, may be compromised by failure of the wall separating the chambers when only one chamber is fired. Therefore, a need exists for a dual chamber gas generator which can produce selective air bag inflation pressurization yet prevent hazardous structural failure of the gas generator. SUMMARY OF THE INVENTION In accordance with the present invention a gas generator comprises two combustion chambers formed within a single housing. Each chamber may be tailored to meet a desired inflation pressure thereby providing selective inflation pressurization. A partition is disposed within the housing to define the two chambers and is positively retained by a dual crimp in the inflator housing to insure the structural integrity of the chambers. Flame propagation from one chamber to the other is precluded thereby preventing inadvertent ignition of a chamber not activated by the vehicle acceleration sensing system. The present invention will be more fully understood upon reading the following detailed description of the preferred embodiment in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a longitudinal cross-sectional view of a gas generator having two propellant chambers defined and separated by a partition that is retained in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) As seen in Fig. 1 of the drawings, a dual chamber gas generator 1 0 having particular utility for use in, for example, an automobile occupant restraint system, comprises a cylindrical housing 1 2 having a plurality of gas discharge apertures 14 therein. A partition 20 is disposed within housing 1 2 intermediate the ends thereof, thereby defining first and second inflator chambers 22 and 24, respectively. Endcaps 26 and 28 at opposite ends of the housing 1 2 close the chambers 22 and 24, respectively, and support separate ignitors 30 and 32, respectively. Filter assemblies 34 and 36 extend longitudinally within the chambers 22 and 24, respectively, for the support of propellant grains 38 and 40, respectively. A pair of filter retainer clips 50 and 52 are disposed on opposite sides of the partition 20. Pre-ignition propellant containers 54 and 56 are disposed adjacent the clips 50 and 52, respectively. In accordance with the present invention, the partition 20 is retained in position by dual annular crimps 60 and 62 so as to positively preclude a flame front from passing from one chamber to another. The partition 20 is preferably formed from metal or ceramic and is orientated in plane perpendicular to the longitudinal axis of housing 1 2. The propellant capacity of each chamber 22 and 24 can be easily tailored by simply sliding the partition 20 to a desired position intermediate the ends of housing 1 2. Once partition 20 is in position, housing 1 2 is roll formed on opposite sides of the partition 20 to fixedly position the partition 20 and to provide sealing between the chambers 22 and 24. The remaining components are then installed as described above. In operation, either chamber 22 or 24, or both, are selectively ignited depending on the input from the vehicle crash sensing system. Combustion gas flows radially outwardly from either propellant chamber 22 or 24, through filter 34 or 36 thence exiting the inflator 1 0 through the apertures 14 in the housing 1 2. Exclusive operation of either chamber is ensured by positively supporting the partition 20 by a crimp on the opposite side of the partition from the pressurized chamber. Therefore, the full longitudinal thickness of the partition is utilized, in compression, to maximize the structural integrity thereof, and to insure positive sealing. It will be understood that the foregoing description of the preferred embodiment of the present invention is for illustrative purposes only, and that the various structural and operational features herein disclosed are susceptible to a number of modifications, none of which departs from the spirit and scope of the present invention as defined in the appended claims.

Claims: WE CLAIM: 1 . A gas generator for a vehicle occupant protection system comprising: an elongated cylindrical housing; a pair of end closures at opposite ends of said housing, respectively; a radially extending partition in said housing intermediate the ends thereof defining a pair of discrete propellant chambers; and a pair of annular crimps in said housing on opposite sides, respectively, of said partition whereby combustion pressure in one of said propellant chambers biases the full longitudinal thickness of said partition against the crimp on the opposite side thereof to maximize sealing therebetween and structural integrity of said partition.

Inventors: ADAMINI CHRIS A, KRUPP ROBERT M, ADAMINI, CHRIS, A., KRUPP, ROBERT, M.
Applicants: AUTOMOTIVE SYSTEMS LAB, AUTOMOTIVE SYSTEMS LABORATORY, INC.
Application year: 2000
Main classification: B60R21
IPC codes: B60R21