The Supplemental Inflatable
Restraint (SIR) system
supplements the protection offered by the driver and front passenger seat
belts. The SIR system deploys an air bag (3) from the center of the steering
wheel and from the right side of the instrument panel.
A frontal crash of sufficient force up to 30 degrees off the center
line of the vehicle will deploy the air bags. The knee bolsters (2) absorb
crash energy. The driver and passenger knee bolsters are below the instrument
panel. The steering column is collapsible.
The SIR system consists of the following components:
| • | An Inflatable Restraint Sensing and Diagnostic Module (SDM) |
| • | An Inflatable Restraint Steering Wheel Module |
| • | An Inflatable Restraint Steering Wheel Module Coil in the turn
signal switch assembly |
| • | An Inflatable Restraint IP Module |
| • | An AIR BAG warning lamp in the instrument cluster |
The deployment loops consist of the following parts:
| • | The inflatable restraint steering wheel module coil |
| • | The inflatable restraint steering wheel module |
| • | The inflatable restraint IP module |
The function of the deployment loops is to supply current through the
inflator modules, which will cause deployment of the air bags. Deployment
occurs when the SDM detects sever vehicle velocity changes.
The SDM contains a sensing device (Accelerometer) that converts vehicle
velocity changes into an electrical signal. The SDM compares this electrical
signal to a value stored in memory. When the generated signal exceeds the
stored value, then the SDM performs additional signal processing and compares
the generated signals to values stored in memory. When two of the generated
signals exceed the stored values, then the SDM will cause current to flow
through the inflator modules, deploying the air bags.
