Air Bag Systems: Description and Operation

OPERATION

FUNCTION OF COMPONENTS





1. FRONT AIRBAG SENSOR
A front airbag sensor is mounted inside each of the front fenders. The sensor unit is a mechanical type. When the sensor detects deceleration force above a predetermined limit, contacts is made in the sensor, sending a signal to the center airbag sensor assembly. The sensor cannot be disassembled.





2. SPIRAL CABLE (in COMBINATION SWITCH)
A spiral cable is used as an electrical joint from the vehicle body side to the steering wheel.





3. STEERING WHEEL PAD (with AIRBAG)
The inflater and bag of the supplemental restraint system are stored in the steering wheel pad and cannot be disassembled. The inflater contains a squib, igniter charge, gas generant, etc., and inflates the bag in case of frontal collision.





4. FRONT PASSENGER AIRBAG ASSEMBLY
The inflater and bag of the supplemental restraint system are stored in the front passenger airbag assembly and cannot be disassembled. The inflater contains a squib, igniter charge, gas generant, etc.. and inflates the bag in case of a frontal collision.





5. SEAT BELT PRETENSIONER
The seat belt pretensioner system is a component of the front seat outer belt. The pretensioner contains a squib, gas generant, wire, piston, etc., and operates in the event of a frontal collision.





6. SRS WARNING LIGHT
The SRS warning light is located on the combination meter. It goes on to alert the driver of trouble in the system when a malfunction is detected in the center airbag sensor assembly. In normal operating condition when the ignition switch is turned to the ACC or ON position, the light goes on for about 6 seconds and then goes off.





7. CENTER AIRBAG SENSOR ASSEMBLY
The center airbag sensor assembly is mounted on the floor inside the console box. The center airbag sensor assembly consists of a center airbag sensor, safing sensor, diagnosis circuit and ignition control, drive circuit. etc.
It receives signals from the airbag sensors, judges whether the SRS must be activated or not.








8. SRS CONNECTORS

All connectors in the supplemental restraint system are colored yellow to distinguish them from other connectors. Connectors having special functions and specifically designed for SRS are used in the locations shown below to ensure high reliability. These connectors use durable gold-plated terminals.





(1) Terminal Twin-Lock Mechanism
Each connector has a two-piece construction consisting of a housing and a spacer. This design secures the locking of the terminal by two locking devices (the retainer and the lance) to prevent terminals from coming out.








(2) Airbag Activation Prevention Mechanism
Each connector contains a short spring plate. When the connector is disconnected, The short spring plate automatically connects the power source and grounding terminals of the squib.





HINT: The illustration shows connectors 4, 5, and 1O. Connectors 1 and 8 have short spring plates on the female terminal side, and connectors 3, 9 and 11 have different shapes. These operating principles are the same.

(3) Electrical Connection Check Mechanism
This mechanism is designed to electrically check if connectors are connected correctly and completely. The electrical connection check mechanism is designed so that the connection detection pin connects with the diagnosis terminals when the connector housing lock is in the locked condition.





HINT: The illustration shows connectors 2 and 7. Connectors 1 and 8 also have the same operating principle.

(4) Connector Twin-Lock Mechanism
With this mechanism connectors (male and female connectors) are locked by 2 locking devices to increase connection reliability. If the primary lock is incomplete ribs interfere and prevent the secondary lock.








When the vehicle is involved in a frontal collision in the hatched area (Fig. 1) and the shock is larger than a predetermined level, the SRS is activated automatically. A safing sensor is designed to go on at a smaller deceleration rate than the front and center airbag sensors. As illustrated in Fig. 2, ignition is caused when current flows to the squib, which happens when a safing sensor and a front airbag sensor and/or the center airbag sensor go on simultaneously. When a deceleration force acts on the sensors, four squibs in the seat belt pretensioners (LH, RH), driver airbag and front passenger airbag ignite and generate gas. The gas in the seat belt pretensioners forces down the piston to tension the wire, thus making the seat belt retractor roll up the seat belts. The gas discharging into the driver and front passenger airbags rapidly increases the pressure inside the bags breaking open the steering wheel pad and instrument panel door. Bag inflation then ends, and the bags deflate as the gas is discharged through discharge holes at the bag's rear or side.