Description & Operation: Notes
The Supplemental Restraint System (SRS) is designed to operate when vehicle strikes a rigid or heavy object with enough force to activate SRS. Activation impact area is directly in front of vehicle and 30 degrees on either side of dead center. SRS is not designed to activate during a side or rear collision, a rollover, or a frontal collision at low speed or with soft objects. In addition vehicle is equipped with Side Impact Protection System (SIPS). SIPS are seat mounted air bags which deploy only in the event of a side impact intrusion in the front passenger compartment.
Main SRS components include a driver-side air bag/gas generator module mounted to steering wheel, and passenger-side air bag/gas generator module mounted to instrument panel. System also includes a contact reel (clockspring) mounted to steering column, under steering wheel, sensor module, mounted under center console and SRS warning light, mounted in instrument gauge cluster light bar. See Fig 1. Vehicle is also equipped with pyrotechnical seat belt tensioners for driver and front passenger seats. Seat belt tensioners are mounted inside B-pillars. For SRS to operate properly, 3-point seat belts must be worn.
If vehicle's deceleration rate, as recorded by sensor module, is sufficiently high, sensor module delivers voltage signal to ignite gas generators in air bag module and in seat belt tensioners. When air bag module gas generator is ignited, a quantity of non-toxic nitrogen gas is produced, filling air bag in a few hundredths of a second. Immediately after air bag inflates, gas is released through a ventilation hole on rear of air bag module. Entire sequence of air bag inflation and collapse takes about 0.2 second.
Seat belt tensioners are connected to seat belt reel by a cable. When seat belt tensioner is activated by sensor module, belt is tightened about 4". In a collision, seat belt tensioners tighten seat belts instantly, holding occupant tightly against seat back.
SIPS units are mounted on the outer sides of both front seats. See Fig 2. The SIPS main components are deployment sensor units and SIPS air bag modules. Deployment sensors face doors, deploying air bags when a side intrusion impact is detected. Only SIPS on affected side of vehicle will deploy. SIPS sensor does not sense deceleration or "G" forces. An impact of at least 6.6 ft/sec (2m/s) is necessary to trigger SIPS sensor. This prevents unnecessary activation by light blows from outside objects. In event of a side collision, deformation of door will push it into proximity with a cover plate over SIPS sensor. Sensor cap will deform, detonating a firing pin and sending a shock wave through tubes inside the seat frame. When seat air bag module is excited by this impulse, powder charge inside gas generator ignites. This produces nitrogen gas to fill and expand side air bag cushion. One gas generator ignites immediately, the second generator being delayed about 3 milliseconds. Delay is designed to maintain pressure and volume for sufficient time, to gain maximum effect from deployment. Cushion will break open SIPS cover and rip seat upholstery seam. Cushion will then inflate toward door panel to help protect occupant's rib cage. After deployment, cushion will deflate through integral gas vents. No warning lamp or diagnostic system is used on SIPS modules.