TIAGO

SUPPLEMENTARY RESTRAINT SYSTEM (SRS)

11.1.6.2.4. RPLL BELTS

RETRACTOR PRETENSIONER LOAD LIMITOR:

Seatbelt pre-tensioner is a device installed in

vehicles to reduce slack that may exist in a

seatbelt system at the moment of a frontal

collision. Having the seatbelt system snug allows

the supplemental restraint airbag system to work

most effectively. A loose seatbelt system does not

keep the occupant in the proper position during the

forces of a crash. In order for airbags to reduce or

eliminate injury, the occupant must be seated,

belted and in the correct position in the vehicle.

Pretensioner device is mounted in the retractor

unit. The Pretensioner unit essentially consists of a

ball cage comprising of a tube of steel balls

surrounding a toothed wheel. The wheel is

mounted on the belt-webbing spool.

When the ECU senses a crash, depending on the

crash severity, it sends a "fire" signal to the squib

in the belt Pretensioner. The firing of the squib

causes displacement of the balls in the tube. The

movement of the balls causes rotation of the

toothed wheel, which in turn rotates the webbing

spool and removes the slack from the belt.

LOAD LIMITOR

In high speed frontal crashes, passenger moves

forward due to inertia at a very high speed. If the

seat belt gets locked during such crashes it may

cause injuries to the passenger as he is forcibly

held by the seatbelt against the inertia force.

Load limiters are provided to limit the seat belt

loads to a pre-defined value. Load limiters are to

be used only in airbag equipped vehicles. The load

limiter fitted inside the retractor unit is basically a

torsion bar. Whenever the belt load increases

beyond the pre-defined limit, some length of the

belt is released due to twisting of the torsion bar.

The activation of the load limiter does not depend

on signal from the ECU.