Multi-chamber passenger air bag cushion with interchamber venting

Abstract: The air bag (10) is divided by a fabric sheet (32) including vent holes (24, 26) into an upper chamber (20) and a lower chamber (18). Instead of the vent holes (24, 26) venting may be provided by permeability of the sheet (32). The sheet is sewn to the mouth (28) and an intermediate region (29) of the bag. The sheet functions as a tether to limit and direct the deployment of the air bag as well as to provide shape to the deployed bag. Gas from an inflator (16) is directed into the lower chamber (18) then passes through vent holes (24, 26) into the upper chamber.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to inflatable occupant restraint systems for the passenger side of automotive vehicles, and more particularly, to a multi-chamber air bag having utility in such systems. 2. The Related Art It is known in the prior art, as disclosed in U.S. Patent No. 3,642,303 granted to F. J. Irish et al., to provide an occupant restraint system comprising a plurality of bags which are inflated on vehicle impact with another vehicle or object. A first one of the bags receives the impact of the occupants' torso. A second one of the bags receives the impact of the occupants' head, the second bag being secured to the top of the first bag. The first one of the bags has controlled pressure relief to prevent excessive movement between the occupant's head and torso. This document forms the preamble of claim 1. While such a system involving a plurality of bags can provide effective cushioning of a vehicle occupant, a multiple bag system could prove very difficult to construct because of lack of proper access to the interior of the upper or outer bag as needed for the stitching required to sew the two bags together, or more specifically, to sew the head bag to the top of the torso bag. Thus, there is a need and a demand for improvement in such air bag occupant restraint systems, particularly for the passenger side of vehicles, having separate portions designed to be impacted by the occupant's torso and head (or head and shoulders), respectively, while facilitating the construction thereof, reducing the cost of fabrication, and increasing the reliability. The present invention was designed to fill the technlological gap that has existed in the art in these respects. SUMMARY OF THE INVENTION An object of the invention is to provide an improved vehicle occupant restraint system comprising a multi-chamber air bag having a first chamber for absorbing the impact of the occupant's torso and a second chamber for absorbing the impact of the occupant's head and shoulders and which is characterized by the ease of construction thereof, reduced cost of fabrication, and increased reliability. According to the invention there is provided a multi-chamber passenger air bag cushion as claimed in claim 1. In accordance with the invention, the objectives are accomplished by securing in any suitable manner as by stitching a fabric sheet of air bag material to the mouth, that is, the inflating gas inlet opening, and the interior wall of a relatively large air bag thereby dividing the air bag into two chambers. In the deployment of the air bag according to the invention, the initial flow of gas from an inflator is directed into the lower chamber of the air bag, which chamber fills quickly and directs the bag deployment in a downward direction. The pressurized lower chamber supports the majority of the upper body mass of a passenger in the vehicle during the onset of a crash. The quick deployment restrains the abdominal area of the passenger before the passenger's velocity relative to that of the vehicle is increased significantly. Thereafter, the gas is vented to the upper chamber of the air bag, allowing for a more uniform resistance of the torso region by venting out gas as the internal pressure increases and supplying gas to the upper chamber to cushion the head and shoulder region of the passenger. The gas venting between chambers is provided through discrete vents and/or a permeable membrane which separates the chambers. Additional venting can be provided from the upper chamber to reduce rebound during a crash. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. BRIEF DESCRIPTION OF THE DRAWINGS With this description of the invention, a detailed description follows with reference being made to the accompanying figures of drawing which form part of the specification, in which like parts are designated by the same reference numbers, and of which: Fig. 1 is a schematic side elevational view of a fully deployed multi-chamber air bag according to the invention; Fig. 2 is a fragmented side elevational view in the forward part of an automotive vehicle showing the air bag of Fig. 1 in an initial stage of deployment during a crash; Fig. 3 is a fragmented side elevational view similar to Fig. 2 showing the pressurized lower chamber of the air bag supporting the majority of the passenger's upper body mass during the onset of a crash; and Fig. 4 is a fragmented side elevational view similar to Fig. 3 showing the upper chamber pressurized also to cushion the head and shoulders of the pasenger, such pressurization being caused by gas being vented into the upper chamber from the lower chamber. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the multi-chamber air bag of the invention comprises a relatively large air bag 10 which normally is stowed in a collapsed, folded condition in an air bag module canister 12 that is positioned on the instrument panel 14 of a vehicle opposite the passenger seat. While the canister 12 and gas generator or inflator 16 contained therein may include any known canister and gas generator or inflator provided for use with a passenger side air bag restraint system, a preferred form of canister 12 and associated inflator 16 that may be employed is that disclosed in the application for US-A-5 332 256, filed February 24, 1992 by Donald R. Lauritzen and Bradley W. Smith and assigned to the assignee of the present invention. The multi-chamber air bag 10 of the invention is shown in fully deployed condition in Fig. 1. As shown, the air bag 10 includes a lower chamber 18 and an upper chambr 20. The two chambers 18 and 20 have a common wall 22 which allows a gas flow or venting between the chambers 18 and 20 through inter-chamber vents 24 and 26 provided therein. Fabrication of the multi-chamber air bag 10 is accomplished by sewing a sheet of fabric 32 of air bag material between the upper edge of the mouth 28 and an intermediate region indicated at 29 around the air bag interior wall 30 opposite thereto, such fabric forming the common wall 22 which divides the air bag 10 into lower chamber 18 and upper chamber 20. In addition to dividing the air bag 10 into two chambers, the fabric sheet 32 functions as a tether 34 which limits and directs the deployment of the air bag 10, causing the air bag 10 to rotate into place as it is deployed. The tether 34 also provides shape to the deployed air bag 10. Separation of the single air bag 10 into multiple chambers 18 and 20 using a tether is a simple construction because the mouth 28 of the air bag 10 is the access for stitching. As the air bag 10 is deployed, responsively to the onset of a crash, the initial flow of gas from the inflator 16 is directed into the lower chamber, which fills quickly and directs the bag deployment downward as shown in Fig. 2. The pressurized lower chamber supports the majority of the passenger's upper body mass during the onset, that is, the initial stage, of the crash, as illustrated in Fig. 3. This quick deployment of the air bag 10 restrains the abdominal area of the passenger before the passenger's velocity relative to that of the vehicle is increased significantly. Thereafter, the gas in the lower chamber 18 of the air bag 10 is vented to the upper or top chamber 20 of the air bag 10. This allows for a more uniform resistance of the torso region of the passenger by venting out gas as the internal pressure increases and supplying gas to the upper chamber 20 to cushion the head and shoulder region of the passenger, as illustrated in Fig. 4. The gas venting between chambers 18 and 20 is provided through discrete vents 24 and 26 and/or a permeable membrane (not shown) which separates the chambers 18 and 20. Additional venting can be provided from the upper chamber 20 by a vent 36, as illustrated in Fig. 1 to reduce rebound during a crash. The invention is characterized in that critical parameters regarding air bag performance (i.e., femur loads, chest Gs and passenger head injury criteria (HIC)) are improved by quicker inflation of the lower chamber 18 of the air bag combined with venting to the upper chamber 20. Air bag deployment is kept low in front and mid mount modules and remains low in the interchamber venting of gas. In a top mount system, the quicker inflation and interchamber venting would help to quickly and correctly position the air bag. Low deployment of the air bag could also improve results in the out-of-position child tests. Another aspect in respect of which this invention is beneficial is that it allows for greater tailoring ability in order to optimize air bag performance by changing interchamber vent characteristics, chamber volumes and chamber proportions. Thus, in accordance with the invention, there has been provided an improved vehicle occupant restraint system comprising a multi-chamber air bag having a first chamber for absorbing the impact of the torso of a passenger in a vehicle and a second chamber for absorbing the impact of the head and shoulders of the passenger, which system is characterized by the ease of construction thereof, the reduced cost of fabrication, and increased reliability. There has also been provided in accordance with the invention a multi-chamber air bag in which the separate chambers have a common wall which allows gas flow or venting between chambers, which common wall functions, additionally, as a tether to limit and direct the deployment of the air bag to provide shape to the deployed air bag.

Claims: A multi-chamber passenger air bag cushion comprising; (a) an air bag (10) having a mouth (28) for the ingress of inflating gas, which air bag when inflated forms an interior chamber having an inner wall (30), said mouth having an upper edge, (b) a fabric sheet (32) secured to the inner wall (30) of said air bag, dividing said chamber into a multi-chamber air bag having a lower chamber (18) and an upper chamber (20) in which air bag said upper chamber and said lower chamber have a common wall (22) formed by said fabric sheet, whereby inflating gas entering said mouth (28) fills and pressurizes said lower chamber (18), and (c) vent means (24, 26) in said fabric sheet (32) for relieving the pressure of the inflating gas in the lower chamber (18) by allowing the flow therethrough into said upper chamber (20) of the inflating gas for the pressurisation of said upper chamber, whereby said fabric sheet (32) is secured interiorly of said air bag and functions as a tether to direct deployment of said air bag and to shape the deployed air bag whereby as said air bag is deployed, the initial flow of gas entering said mouth (28) is directed into said lower chamber (18) which fills quickly and directs the bag deployment downward so that the pressurized lower chamber supports the majority of the passenger's body mass during the onset of a crash and the quick deployment restrains the abdominal area of the passenger before the passenger's velocity relative to that of the vehicle is increased significantly, and thereafter the gas is vented to the upper chamber (20) of the air bag, allowing for a more uniform resistance of the torso region by venting gas out through said venting means (24, 26) from the lower chamber (18) as the internal pressure therein increases and supplying gas to the upper chamber (20) to cushion the head and shoulder region of the passenger, characterized therein that the fabric sheet (32) is secured between said upper edge of said mouth (28) of said air bag and an intermediate region (29) of said inner wall (30) in opposition to said mouth (28). A multi-chamber passenger air bag cushion (10) as defined by claim 1 wherein said fabric sheet (32) is secured interiorly of said air bag between said upper edge of said mouth (28) of said air bag and said intermediate region (29) of said inner wall (30) by stitching. A multi-chamber passenger air bag cushion (10) as defined by claim 1 or 2 further including means (36) for venting said upper chamber. A multi-chamber passenger air bag cushion (10) as defined by claim 1, 2 or 3 wherein said venting means (24, 26) included in said fabric sheet (32) comprises at least one vent hole (24, 26). A multi-chamber passenger air bag cushion as defined in claim 1, 2 or 3 wherein said venting means included in the fabric sheet (32) is provided by the fabric sheet (32) being a permeable membrane.

Inventors: ORME BRADLEY L, ORME, BRADLEY L.
Applicants: MORTON INT INC, MORTON INTERNATIONAL, INC.
Application year: 1993
Main classification: B60R21
IPC codes: B60R21