Air Bag: Description and Operation
Drivers Airbag ModuleThe driver's airbag is of a two-stage design and attached to the steering wheel by two captive bolts. Electrical connection to the MRS control unit is provided via the rotary coupler. The fully inflated airbag has a capacity of 57 liters. Once the airbag is fully inflated, vents in the airbag prevent further pressure build-up, so that progressive deceleration is provided as the driver contacts the cushion and injury due to sudden impact forces is prevented. The design of the airbag is 'tuned' to match the crush characteristics of the vehicle as well as the steering wheel and collapsing steering column behavior.
Passenger Airbag Module
The passenger front airbag module is located above the stowage tray, directly in front of the passenger seat. The airbag module is mounted to the body cross car beam by means of four Torx bolts, which are capable of withstanding the forces of deployment. The airbag container is a pressed steel fabrication that is designed to withstand the high rate of pressurization.
The unit contains a gas generator and igniter module, which incorporates the nitrocellulose igniter charge and pressurized gas chambers surrounded by a filter screen. The filter prevents solid combustion by-products from entering the airbag during deployment. A link lead connects the airbag module to the main vehicle harness. The other end of the link lead terminates in a squib connector on the left hand side and a squib connector on the right hand side of the passenger airbag module.
Only disconnect the connectors from the airbag module if the airbag module is being removed, otherwise disconnect at the harness end of the link lead.
To disconnect the link lead at the airbag module end, lift the locking cap of the connector to unlatch, and then pull the connector away from the module. Do not pull on the link lead harness. When reconnecting, ensure the connector is fully mated in the socket of the airbag module then press the hinged locking cap into place to secure the connector in position.
The front of the airbag module has a strong paper cover which ruptures when the airbag is deployed. The unfolding airbag then breaks the deployment door perforations in the front fascia; the deployment door remains attached to the fascia by a plastic hinge on its upper inside edge.
Once free of the housing and fascia the airbag inflates to its full extent to provide a protective cushion between the front seat passenger and the fascia/windshield. Vents in the airbag prevent excess pressure bursting the bag and, as soon as the material in the gas generator is exhausted, the airbag deflates. The passenger front airbag has a capacity of 110 liters.
Side (Thorax) Airbag Modules
The driver and passenger side (thorax) airbags are mounted to the front seat backrest frame and are designed to protect the ribs and upper internal organs during side impacts. The modules are side specific (i.e. a right hand module must be fitted to a right hand seat and a left hand module must be fitted to a left hand seat). The side airbags are activated by a control signal from the MRS control unit in the event of a side impact or a front angled impact of sufficient severity to cause both front and side airbag deployment.
The side (thorax) airbag module is consists of a molded plastic case which houses a folded nylon fabric bag, the gas generating capsules and an igniter squib. The rear of the side airbag module features two studs that are used for mounting the module to the seat frame and are secured in position by two nyloc nuts.
The side airbag modules have a fly lead which terminates in a 2-pin connector. The connector connects to the control unit via the main harness and is located beneath the seat.
The side airbag has a capacity of 10.5 liters.
Advanced Head Protection System (AHPS2)
The head airbag, known as the Advanced Head Protection System (AHPS2) offers the vehicle occupants in the front and rear additional protection from impacts. The airbag is located behind the interior trim above the door and rear side glass. The igniter/gas generators are fixed to the body rear inner side panels in the luggage compartment. The airbag itself is tethered to the body by two securing straps and bolts, one at the A post, the other on the C post. In between the two tether points, the airbag is held in place with six plastic clips, which are designed to break apart as the airbag inflates. The center portion of the folded airbag is retained on a metal bracket which itself is secured to the body by two bolts and located at the top of the B post.
The 15 litre head airbag is filled with nitrogen/argon gas from a pressurized chamber and remains inflated slightly longer than conventional airbags, this is to provide additional head protection in the event of a secondary impact.
To disconnect the vehicle harness lead from the gas generator, lift the locking cap of the connector to unlatch and then pull the connector away from the module. Do not pull on the harness lead. When reconnecting, ensure the connector is fully mated in the socket of the airbag module then press the hinged locking cap into place to secure the connector in position.