Air Bag Systems: Description and Operation

GENERAL DESCRIPTION
The airbag system consists of an airbag control module, left and right front sub sensors, an electric sensor and safety sensor built into the control module, driver's and passenger's airbag modules each containing an inflator and airbag, and side airbag sensors and modules each containing an inflator and airbag.

Front airbag system:
A frontal impact exceeding the set level causes the safety sensor, electric sensor and one or both front sub sensors to input signals to the CPU. The CPU determines whether the airbags should be inflated or not based on these signals.

Side airbag system:
Input of a side impact signal showing shock energy greater that the set level causes the airbag on the corresponding side to inflate.







AIRBAG CONTROL MODULE
The airbag control module is installed in front of the front floor tunnel. It detects the vehicle's deceleration by receiving electrical signals from its inside safely and electric sensors as well as the front sub sensors and judges whether to inflate the airbags. This control module has a built-in self-diagnosis function. If a fault occurs inside the system, it lights up the airbag warning light in the combination meter. The fault data is stored in the control module. A back-up power supply is provided for possible damage to the battery during an accident, and a boosting circuit is built into the control module in case of a battery voltage drop.







AIRBAG SENSOR
The airbag control module and side airbag sensor contain an electric sensor and a safety sensor.

The electric sensor consists of a semiconductor type sensor which senses the deceleration caused by collision in terms of change in the electrical resistance of the impact sensing circuit.

The safety sensor is a pendulum type sensor. If the sensor receives a frontal or side impact exceeding a certain limit, the mass in the sensor move in the direction opposite to the impact direction to turn the switch ON.




AIRBAG MODULES







DRIVER'S AIRBAG
The driver's airbag module is located at the center of the steering wheel.The module contains an airbag and an inflator. If a collision occurs, the inflator produces a large volume of gas to inflate the airbag in a very short time.







PASSENGER'S AIRBAG
The passenger's airbag module is located at the upper portion of the instrument panel. The module uses a 2-stage inflator to control the output of the inflator.

The 2-stage inflator houses two igniters and gas heating agents, together with compressed gas inside a metal container. The airbag sensor system detects the magnitude of the impact caused by the collision, and controls the ignition timing of the inflator.







1. If a collision occurs at low to mid speed, the inflator is ignited in 2 stages.
By delaying the ignition of the 2nd stage gas heating agent, the output of the inflator is reduced.
2. If a collision occurs at a high speed, both stages of the inflator are ignited simultaneously. The gas heating agent for the 1st stage and the 2nd stage are ignited at the same time.
By optimizing the airbag deployment according to the condition as explained above, the passenger restraint operation at low to mid speeds is improved.







SIDE AIRBAG
A side airbag module is located at the outer side of each front seat backrest, and it contains an airbag and an inflator.

If a side-on collision occurs, the inflator produces a large volume of gas to inflate the airbag in a very short time.


AIRBAG CONNECTORS

DESCRIPTION
The airbag system uses connectors with a double lock mechanism and an incomplete coupling detection mechanism for enhanced reliability. If coupling is incomplete, the airbag warning light comes on in the combination meter.







STEERING ROLL CONNECTOR
The steering roll connector is located between the steering column and steering wheel. The connector contains a spirally wound flat cable. The cable can follow rotational movements of the steering wheel and ensures connection between the airbag module in the steering wheel and the airbag harness through which electrical signals are transmitted from the airbag control module.







AIRBAG WARNING LIGHT
The airbag warning light is located inside the combination meter. It illuminates if a poor connection in the airbag circuit occurs, or if the airbag control module detects an abnormal condition. When the airbag system is normal this light comes on when the ignition switch is turned ON and then goes out about 7 seconds later



WIRE HARNESS
The airbag harnesses are integrated into the body harness as follows:
- Front sub sensor harness; integrated into the front harness.
- Airbag main harness: Integrated into the bulkhead harness.
- Pretensioner and side airbag harnesses: Integrated into the rear harness.