Restraint systems (Description): Description and operation

DESCRIPTION

The airbag Supplementary Restraint System (SRS) is a safety device which, when deployed in the event of a severe frontal impact, provides additional protection to the driver’s face and upper torso. The airbag is designed to inflate when the vehicle is exceeding a set speed and receives a frontal impact within the area shaded.

The pre-tensioner consists of the seat belt buckle and stalk, a piston and a pyrotechnic device. The pre-tensioners, fitted to both driver and passenger seat belt mechanisms are designed to remove any play in the the lap and diagonal belts in the event of a severe frontal impact.

OPERATION

CAUTION: The diagnostic control unit is a non-serviceable component and no attempt should be made to repair or modify the unit.

The diagnostic control unit (DCU) which is mounted within the passenger compartment performs two functions:

1. It continually monitors the airbag system for faults;
2. It provides a fire signal to the airbag and pre-tensioners in the event of a crash.

The SRS warning lamp illuminates to inform the driver of any airbag system faults and during a system self test.

The diagnostic control unit comprises of the following circuits which control the airbag system:

1. The crash sensor determines the severity of any impact and can discriminate between rough road conditions and an actual crash.
2. The safing sensor is wired in series with the crash sensor. The fire signal from the crash sensor therefore, passes through the safing sensor which confirms a crash is taking place.
3. The regulator circuit maintains stability of the system in the event of battery voltage drop.
4. The back-up power supply provides power to the system in the event of the battery being damaged or disconnected during the impact.