Restraints and Safety Systems: Description and Operation

The Air Bag-Supplemental Restraint System (SRS) is designed to supplement driver seat belts during front-end collisions, reducing the risk of serious injury or death. Two collision-sensitive sensors are located in the Air Bag Diagnostic Unit (ADU). These two sensors (Safing sensor and G-sensor) are electrically connected to the air bag and the battery.

In case of a frontal crash, the G-sensor receives collision deceleration information. The collision deceleration information is converted into digital data and transmitted to the CPU (Central Processing Unit). The CPU calculates the digital data and compares them with preprogrammed data to determine whether it has to send a signal to deploy the air bag module or not. If the calculation of the CPU corresponds to the preprogrammed data, a deployment signal is sent. At the same moment, the safing sensor, which is linked linearly on the deployment circuit, checks whether the deceleration has occurred due to an actual collision, or by other electronic waves and anomolies. So, the air bags will only deploy with a deployment signal from the CPU and closing of sating sensor switch.

The Driver is protected by a steering wheel mounted air bag. The Air bag-Supplemental Restraint System consists of an Air Bag Module, Air Bag Diagnostic Unit, and wire harness & clock-spring assembly.

The driver air bag module consists of a bag cover, air bag, retainer ring, retainer housing and inflator.

The passenger air bag module consists of a deployment door, air bag assembly, inflator and retainer housing. Because of size difference, the passenger air bag module incorporates a larger, tubular shaped inflator.

The driver air bag cover is made of TPE (Thermos Plastic Elastomer), and it splits along a tear seam in the event of a collision. The air bag itself is made of Nylon 66, and the face contact surface is coated with silicone. A vent hole is provided at back side of air bag to deflate air bag immediately after inflation so that it does not interfere with the drivers vision. The inflator produces nitrogen gas by igniting solid propellant pellets inside inflator. The ignitor is triggered by an electrical current and the ignitors ignition intensifier, which in turn ignites propellant pellets causing the air bag to deploy. A heat sink and filter within the unit cools and filters nitrogen gas as it enters air bag.

Air Bag Diagnostic Unit (ADU) consists of a CPU, memory, auxiliary power supply and G-sensor and safing sensor. An auxiliary power supply is installed to ensure air bag deployment if battery power is lost in a collision.

The CPU not only initiates air bag deployment but also performs the SRS self-test. CPU initiates a test sequence every time ignition key is turned "ON" and the Air Bag Indicator is illuminated for 4 - 6 seconds. When the self test sequence is completed and no fault is found, lamp goes out. If any failure is detected, the warning lamp will stay "ON" or flash to warn driver. Even while driving, the CPU continually monitors circuits and components of air bag system. If a failure occurs within system while driving, the warning lamp is immediately illuminated. Details of those detected failures are stored in memory and can be retrieved with Kia Power Scan Tool.

The clock spring assembly is incorporated into the combination switch to provide a positive connection between vehicle wire harness and driver air bag module while allowing sufficient rotation for vehicle steering. This assembly is also replaced as a complete assembly only.

The Air Bag electrical connector has a shorting bar which will short across Air Bag assembly circuits when the Air Bag connector is disconnected. The Air Bag circuit is automatically shorted by the shorting bar in this way to help prevent unwanted deployment of the Air Bag when servicing the instrument panel, Air Bags or other SRS components.