HEXA

SUPPLEMENTARY RESTRAINT SYSTEM (SRS)

24.7 COMPONENTS

A RESTRAINT WITHOUT AIRBAGS

Restraints system without airbags consists of follow-

ing main components:



Seat Belt.



Emergency Locking Retractor (ELR).



Micro-switch.

I. SEAT BELT

With these seat belts occupants have to buckle the

seat belts before starting to drive the vehicle.

II. EMERGENCY LOCKING RETRACTOR (ELR)

It is a locking mechanism which is activated in follow-

ing conditions:



When a sudden deceleration is sensed



When the seat belt webbing pull-out speed ex-

ceeds a threshold value



When one side of the vehicle is more inclined

than the other side.

e.g. If one of the vehicle tyre goes off-road during

driving.

III. MICRO-SWITCH / SEAT BELT REMINDER

WARNING LAMP

Micro switch is a device which indicates the whether

the seat belt is engaged or not. This switch activates

the warning light

(which is in the instrument cluster

) if

the seat belts are not worn or not buckled properly.

B RESTRAINT WITH AIRBAGS

I ECU

The SRS ECU

gets power supply from vehicle

battery

and

is designed to perform the following

functions in the air bag system:

FUNCTIONS

ENERGY RESERVE

SRS ECU

maintains a Reserve energy supply to

provide deployment energy after ignition voltage is

lost during crash. However, the energy reserve is for

a limited duration, therefore battery terminals and its

connection to airbag ECU needs to be checked.

CRASH DETECTION

SRS ECU

monitors vehicle deceleration levels to

detect crashes which are severe enough to warrant

deployment.

AIR BAG DEPLOYMENT

When sensors detect a crash of sufficient severity, it

sends signal to the SRS ECU which in turn sends

signal to the air bag (inflator) modules for deploy-

ment.

LAMP CONTROL AFTER FIRST CRASH:

“AIR BAG” warning lamp is turned and kept ON.

SRS ECU needs replacement if it has sensed a

crash.