DUAL CHAMBER INFLATOR

Abstract: A dual chamber inflator (10) utilizes a housing (12) having two combustion chambers (14 and 16), contained within a monolithic body (18). A partition (32) integral to the monolithic body (18) and centrally disposed thereof forms two discrete propellant chambers (14 and 16) in fluid communication with the housing (12).

Description: DUAL CHAMBER INFLATOR BACKGROUND OF THE INVENTION The present invention relates to gas generators, used to inflate air bags in a vehicle occupant protection system for example, and more particularly, to an improved dual chamber gas generator containing an improved structure for isolating the propellant chambers of a dual chamber inflator so as to ensure proper deployment of the airbag. 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. A firing circuit typically triggers the gas generator 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 U.S. 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 Complete isolation of the chambers of a dual chamber airbag inflator is critical to soft deployment of the airbag. Accordingly, the present invention relates to an improved structure for isolating the propellant chambers of a dual chamber inflator so as to insure proper deployment. Specifically, a cup shaped impact extrusion having a central partition, is employed to define the dual chambers of the inflator and positively isolate the propellants therein. The impact extrusion is a structural component of the inflator pressure vessel. The inflator can be configured to ignite the propellants in the dual chambers simultaneously or with a delay between ignition depending on the severity of the crash. BRIEF DESCRIPTON OF THE DRAWINGS Figure 1 is a top view, partially in cross-section, of a two-chamber inflator in accordance with the present invention. Figure 2 is a cross-sectional view taken along the line 2-2 of Figure 1 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION As seen in Fig. 1 of the drawing, an inflator 1 0, in accordance with a preferred embodiment of the present invention, comprises a housing 1 2, propellant chambers 14 and 1 6 defined by an impact extrusion 1 8, disposed centrally of the housing 1 2, an annular filter 20 and a pair of igniters 22 and 24. The inflator housing 1 2 is formed by bonding or welding two sections 25 and 26 to one another in nested relationship. The lower housing portion 26 contains an aperture 38 for the acceptance or coupling of the impact extrusion 1 8. In general, extrusion 1 8 is welded to housing 1 2 at aperture 38. The extrusion 1 8 is provided with an integral centrally disposed partition 32 and a pair of igniter and propellant support tubes 34 and 36 for the support of the igniters 22 and 24, respectively. The igniter tubes 34 and 36 are welded to section 25, and are provided with a plurality of gas discharge apertures 40 and 41 disposed in a circumferential array at points radially aligned with propellant grains 42 and 44, respectively. The filter 20 comprises a fine wire mesh annulus that is resiliently axially compressed between the housing sections 25 and 26 upon assembly thereof. The filter 20 is radially positioned between the extrusion 1 8 and an inner wall of the housing 1 2. Given that other known manufacturing methods are contemplated, impact extrusion 1 8 is also characterized as a monolithic body or a cup- shaped structure. In essence, the various structural features of the extrusion 1 8 are integrated within a unified structure thereby enhancing the strength and operability of the inflator 10. Stated another way, a cup-shaped structure 1 8 has a plurality of partitions integral thereto, including a first igniter tube 34 and a second igniter tube 36, and, a partition 32 centrally disposed within the housing 1 2. Tubes 34 and 36 are provided for the acceptance of igniters 22 and 24, respectively. Partition 32 separates structure 1 8 into two discrete propellant chambers 14 and 1 6, each chamber comprising at least one aperture 1 5 and 1 7, respectively. Thus, when propellants 42 and 44 are ignited, co-mingling of the resulting combustion gases is prevented and heat transfer is inhibited between the two chambers. When selected, sequential operation rather than simultaneous operation of the two chambers is thereby ensured. In operation, chambers 1 4 and 1 6 are configured to ignite simultaneously or sequentially depending on the input from the vehicle crash sensing system. Combustion gas flows radially outwardly from propellant chambers 14 and 1 6, then through filter 20 thence exiting the inflator 10 through the plurality of apertures 1 3 in the housing 1 2. The wire mesh filter 20 can be formed from multiple layers or wraps of metal screen, for example. Although not limited thereby, U.S. Patent No. 6,032,979, herein incorporated by reference, illustrates a typical metal filter. It will be understood that the foregoing description of the preferred embodiment of the present invention is for illustrative purposes only. For example, the propellants 42 and 44 may alternatively be contained within the chambers 1 4 and 1 6, respectively. As such, 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: WHAT IS CLAIMED IS: 1 . A dual chamber inflator for a vehicle occupant protection system comprising: a housing comprising a first plurality of apertures spaced therein; a monolithic body fluidly communicating with and coupled to said housing, wherein said monolithic body comprises a first integral partition thereby forming a discrete first propellant chamber and a discrete second propellant chamber. 2. A dual chamber inflator for a vehicle occupant protection system comprising: a housing comprising a first plurality of apertures spaced therein; a monolithic body fluidly communicating with and coupled to said housing; and a plurality of partitions integral to said monolithic body, wherein a first integral partition forms a first igniter support having a second plurality of apertures spaced therein, a second integral partition forms a second igniter support having a third plurality of apertures spaced therein, and a third integral partition forms a discrete first propellant chamber and a discrete second propellant chamber, said first and second igniter supports separately contained within said first and second propellant chambers, respectively. 3. A gas generator comprising: a housing comprising a first plurality of apertures spaced therein; a cup-shaped body fluidly communicating with and coupled to said housing; a plurality of partitions contained within said housing and integral to said cup-shaped body, wherein, a first integral partition forms a first igniter support having a second plurality of apertures spaced therein, a second integral partition forms a second igniter support having a third plurality of apertures spaced therein, and a third integral partition forms a discrete first propellant chamber and a discrete second propellant chamber, said first and second igniter supports fluidly communicating with and separately contained within said first and second propellant chambers, respectively; a first propellant within said first igniter support; a second propellant within said second igniter support; a first igniter contained by said first igniter support; and a second igniter contained by said first igniter support. 4. The gas generator of claim 3 further comprising an annular filter fluidly communicating with and radially spaced about said cup-shaped body and within said housing. 5. A gas generator comprising: a housing comprising a first plurality of apertures spaced therein; a monolithic body fluidly communicating with and coupled to said housing; a plurality of partitions contained within said housing and integral to said monolithic body, wherein a first integral partition forms a first igniter support having a second plurality of apertures spaced therein, a second integral partition forms a second igniter support having a third plurality of apertures spaced therein, and a third integral partition forms a discrete first propellant chamber and a discrete second propellant chamber, said first and second igniter supports fluidly communicating with and separately contained within said first and second propellant chambers, respectively; a first propellant within said first igniter support; a second propellant within said second igniter support; a first igniter contained by said first igniter support; and a second igniter contained by said first igniter support. 6. The gas generator of claim 5 further comprising an annular filter fluidly communicating with and radially spaced about said monolithic body and within said housing. 7. A gas generator comprising: a housing comprising a first plurality of apertures spaced therein; an impact extrusion fluidly communicating with and coupled to said housing; a plurality of partitions contained within said housing and integral to said impact extrusion, wherein a first integral partition forms a first igniter support having a second plurality of apertures spaced therein, a second integral partition forms a second igniter support having a third plurality of apertures spaced therein, and a third integral partition forms a discrete first propellant chamber and discrete a second propellant chamber, said first and second igniter supports separately contained within said first and second propellant chambers, respectively; a first propellant within said first igniter support; a second propellant within said second igniter support; a first igniter contained by said first igniter support; and a second igniter contained by said first igniter support. 8. The gas generator of claim 7 further comprising an annular filter fluidly communicating with and radially spaced about said monolithic body and within said housing.

Inventors: QUIOC EDUARDO, QUIOC, EDUARDO
Applicants: AUTOMOTIVE SYSTEMS LAB, AUTOMOTIVE SYSTEMS LABORATORY, INC.
Application year: 2000
Main classification: B60R21
IPC codes: B01J7, B60R21