This invention is related to an air cushion restraint system (ACRS) for providing vehicle occupant protection in the event of a vehicle impact, and particularly, to an air bag construction for providing enhanced strength in the area of the attachment of the air bag to the vehicle support structure.
Impact actuated inflatable occupant restraint systems typically comprise a source of a non-combustible inflating gas and a folded inflatable air bag. A crash sensor is used to detect deceleration of the vehicle due to impact and actuates the inflator. Upon inflation, the bag is deployed to provide a resilient restraint for absorbing the kinetic energy of the occupant's body within the vehicle.
In a typical air cushion restraint system configuration, the inflator unit is mounted to a vehicle support structure, and the air bag, which defines an enclosed volume for receiving the inflation gas, is also attached to the support structure. The inflation gas typically fills the air bag through an inflation gas opening or mouth. The air bag is attached to the support structure around the inflation opening, usually by being clamped between the ACRS housing and a mounting ring. Air cushion restraint systems designed for the driver's side of a motor vehicle are generally packed into the steering wheel whereas the passenger side ACRS is mounted inside the vehicle instrument panel.
Although presently available ACRS systems provide exceptional occupant protection, designers of these systems are constantly striving to increase their level of performance, efficiency, ease of manufacture, etc. One area of continuing development is that of air bag strength. During air bag inflation and when an occupant strikes an air bag, significant gas pressures are developed which impose tension stresses on the bag fabric. In order to operate properly, the air bag structural integrity must be maintained during the impact sequence. In the event that the air bag tears or breaks away from the mounting structure, excessive inflation gas loss rates can occur to the extent of reducing the effectiveness of the restraint system. In air bag testing and development, air bags are often statically pressurized with air to determine the point at which fabric failure occurs. Present U.S. Federal Motor Vehicle Safety Standards (FMVSS) require an air bag to remain intact at an air inflation pressure of at least 19 PSI. During tests to evaluate air bag strength, air bags are often pressurized to failure. The most common failure mode is a tearing of the bag from the support structure at the inflation or mounting opening mouth. Therefore, increasing the strength of the air bag at the inflation opening mouth can in many cases enable the air bag to maintain higher inflation pressures.
This invention is related to an air bag design featuring a reinforced air bag inflation or mounting opening. In accordance with the preferred embodiments of this invention, the air bag features a retainer ring, preferably made of a polymeric plastic material which is sewn to the air bag fabric circumscribing the inflation or mounting opening and includes means for engaging with the restraint support structure.
Most air bag systems in present use today require the use of a reinforcing ring or perimeter frame for clamping the air bag against a mounting structure and require a number of fasteners such as bolts or rivets to be installed around the perimeter frame. The requirement of using a large number of individual fasteners imposes cost penalties, not only due to the cost of the fasteners themselves, but also due to the labor and assembly operations required to install the fasteners.
Another aspect of the present invention is an air bag design featuring enhancements in the manner of assembly which reduce the number of discrete fasteners required around a perimeter air bag mounting frame which must be fastened, while still providing a secure connection between the air bag and the support structure.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.