Pyrotechnic air bag stitch vent

[0002] This invention relates to an occupant restraint system and, in particular, to an occupant restraint system having an air bag cushion with a vent.

[0003] Occupant restraint systems having air bag cushions are well known. During an impact of a predetermined severity, a restraint control module signals the inflator to inflate an air bag cushion to protect an occupant. There are times, however, when the air bag cushion inflates to a higher pressure and creates a larger force than desired or needed such as when the vehicle occupant is out of position or properly belted or when the collision is of a lesser severity.

[0004] Various solutions have been developed to decrease the internal pressure inside the air bag cushion by venting the gas inside the air bag cushion. Automatic vents have been installed on air bag cushions that open when a certain predetermined internal pressure has been reached. One example of such a vent is disclosed in U.S. Pat. No. 5,219,179, issued to Eyrainer et al. In Eyrainer, a predefined relief opening is designed to tear at a predetermined internal air bag pressure to provide damping action. However, other factors, such as a small-statured, buckled, or an out-of-place occupant, may require venting the air bag cushion at a pressure lower than the predetermined pressure of the automatic relief opening and in a more time-controlled manner or fashion. Further, the predetermined relief opening can only open in a set manner creating limited air bag geometries and internal pressures regardless of what the optimum air bag geometry would be for the particular occupant and crash conditions.

[0005] Accordingly, there is a need to provide an air bag cushion that is capable of venting depending on factors such as whether the occupant is buckled, the size and position of the occupant, and the severity of the crash, and that is able to produce multiple air bag cushion geometries and/or internal pressures.

[0006] Accordingly, it is an object of this invention to provide a vehicle occupant restraint system having an air bag cushion venting system that vents based on factors other than a predetermined internal air bag cushion pressure.

[0007] It is another object of this invention to employ an air bag cushion venting system that can provide time-dependent venting at strategic locations and instances in the crash event.

[0008] It is a further object of this invention to provide an air bag cushion venting system that produces variable air bag cushion geometries and controlled internal pressures to accommodate different vehicle occupants under variable conditions.

[0009] Accordingly, this invention features an air bag deployment system for a vehicle having an air bag cushion having at least one pyrotechnic vent, an inflator in communication with the air bag cushion for inflating the air bag cushion, at least one sensor, and a restraint control module electrically connected to the pyrotechnic vent and the at least one sensor. The restraint control module being operative to receive and analyze a signal from the at least one sensor and to signal the pyrotechnic vent to deploy, thereby allowing gas to vent from inside the air bag cushion.

[0010] These and other objects of the invention will be more readily apparent upon reference to the following detailed description.

[0011] FIG. 1 is a view of an occupant restraint system of the present invention having an air bag cushion with a pyrotechnic vent;

[0012] FIG. 2 is a detailed plan view of the pyrotechnic vent of the present invention;

[0013] FIG. 3 is a detailed view of the pyrotechnic vent of the present invention; and

[0014] FIG. 4 is a detailed view of the pyrotechnic vent of the present invention after it has opened.

[0015] Referring now to FIGS. 1-4, an air bag module 1 comprises in its most basic form an inflator 30 and an air bag cushion 10. The air bag cushion 10 is usually stored in a folded state (not shown) to minimize storage requirements. A cover having a tear seam (not shown) generally covers the air bag cushion 10 while it is in its pre-deployed state. During the deployment of the air bag cushion 10, the tear seam tears open and the air bag cushion 10 bursts through the cover to protect the vehicle occupant (not shown). Deployment doors that fold away from deploying air bag cushion may also be used. The inflator 30 inflates the air bag cushion 10 with gas using known methods. However, the exact method of communication between the inflator and the air bag cushion is not relevant to this invention as long as the inflator can inflate the air bag cushion.

[0016] As shown in FIGS. 2 and 3, the air bag cushion 10 comprises at least one pyrotechnic vent 12 on its surface to allow selective venting of gas from inside the air bag cushion 10. The pyrotechnic vent 12 can be made on the air bag cushion 10 itself or preferably manufactured separately and attached to the air bag cushion. The pyrotechnic vent 12 preferable comprises four cutouts 19 that separate the pyrotechnic vent into four flaps 10a, 10b, 10c, and 10deach having a free end 11a, 11b, 11c, and 11d. However, the pyrotechnic vent 12 can also be made with more or fewer cutouts 19 and flaps 10. Stress relief holes 17 may be placed at the end of cutouts 19 to minimize stress and control tearing of the air bag cushion 10 when the pyrotechnic vent 12 opens. A pyrotechnic pouch 20 containing an explosive charge is attached proximate the intersection of the cutouts 19. Preferably, stitching 15 is used to keep the pyrotechnic pouch 20 in place and the four flaps closed for normal deployment of the air bag cushion 10. Other securing means, such as adhesive, may also be used for securing the pyrotechnic pouch 20. An igniter 35 is attached to the pyrotechnic pouch 20 to ignite the explosive charge. An electrical line 25 connects the igniter 35 with the restraint control module 120 which provides the electric charge to cause the igniter 35 to ignite the pyrotechnic pouch 20 and blow open the pyrotechnic vent 12 as shown in FIG. 4.

[0017] During and/or before a collision, vehicle occupant sensors 100 disposed on the vehicle sense various occupant characteristics such as their size, whether or not they are properly belted, if they are out of position, seat on track position, and classification of the occupants including their height and weight. These sensors can include, for example, mechanical limit switches, infrared sensors, ultrasound sensors, photo/vision sensors, and load sensors. Vehicle sensors 110 also disposed on the vehicle sense various vehicle and crash conditions such as the severity of the crash and the speed of the vehicle. A restraint control module 120 receives the signals from the occupant sensors 100 and vehicle sensors 110 and determines, first, if and when the air bag module should be deployed and, second, if additional venting is required.

[0018] If the restraint control module 120 determines that air bag deployment is necessary based on the information sensed from the sensors 100 and 110, the restraint control module 120 signals the inflator 30 to inflate the air bag cushion 10 with gas in a known manner. A minimal amount of gas may vent through cutouts 19 as the air bag cushion 10 inflates.

[0019] If the restraint control module 120 determines that venting is required based on the input from sensors 100 and 110, the restraint control module 120 sends a signal to the igniter 35 via electrical line 25 causing the igniter to detonate the pyrotechnic pouch 20. When the pyrotechnic pouch explodes, the ends of the flaps 10a, 10b, 10c, and 10dare freed and open as shown in FIG. 4 to allow venting. Accordingly, the air bag cushion 10 softens.

[0020] Additional pyrotechnic vents 12 may be placed on the air bag cushion 10 to control the shape and internal pressure of the deploying air bag cushion. For instance, there may be three pyrotechnic vents 12 placed on an air bag cushion 10 in which one or more vents may be employed to control the internal pressure. Based on the information received from the sensors, the restraint control module 120 determines the optimal configuration and internal pressure of the deployed air bag cushion for a particular set of crash conditions and occupant characteristics. By having various pyrotechnic vents 12 on the air bag cushion 10, multiple air bag configurations and internal pressures could be created. Additionally, the restraint control module 120 could control the timing of the opening of the pyrotechnic vents 12 to provide the optimally shaped and pressurized air bag cushion 10 for the particular conditions.

[0021] The amount of venting can be tuned by, for example, modifying the size of cutouts 19 and flaps 10 to create larger or smaller pyrotechnic vents 12, the position of the pyrotechnic vents 12, the number of vents, and the timing of the detonation of the pyrotechnic pouches 20.

[0022] While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.