SEAT BELTS AND ACCESSORIES

Description 7065

SPECIFICATIONS

The vehicle is fitted with seat belts with three mounting points, even for the third rear passenger, with an automatic inertia reel.

The seat belts for the front seats are fitted with electrically controlled pretensioners with a load restricter.

There is a sensor incorporated in the belt mounting housing which gives a warning that the seat belt is not fastened with a warning light in the instrument panel coming on and a buzzer.

The rear seats have seat belts with an inertia reel, located in the pillars and a load limiter (on the reel) with three point mountings for the side seats, whilst the middle seat has a seat belt with a three point mounting and an inertia reel housed in the rear seat backrest.

Front belts with pretensioner and load limiter

Activation of the seat belt pretensioners is controlled by the same strategy as the air bags. They have the function of recovering any slack in the seat belt and retaining the occupant from the very start of the impact by reducing the overall movement of the occupant inside the passenger compartment.

The pretensioners are fitted on the reel. The belts are also fitted with load limiters that lessen the force transmitted by the belts on the chest, coupled, for the front seats, with the air bags with the function of restraining the occupant in the case of an impact.

Front seat belts with pretensioners

Specifications

The pretensioners are pyrotechnic devices that are activated electrically by means of a signal from the electronic control unit. They are built into the reel of the front seat belts. Activation of the seat belt pretensioners is controlled by the same strategy as the air bags.

The pretensioners are designed to take up slack in the seat belt to ensure it holds the occupant against the backrest from the first moments of impact, thus reducing movement inside the passenger compartment.

The seat belts are also fitted with load limiters which decrease the force transmitted by the belts to the chest: the force level at which the limiters act is sufficient to considerably reduce the risk of fracturing shoulder blades and ribs, even in people with brittle bones (e.g. the elderly).

Operation

The following figure shows the pretensioner mechanism.

1 - Gas generator

2 - Electrical connector

3 - Belt

4 - Reel

When the car decelerates to a sufficient extent, as measured by system acceleromters, the electronic sensor in the electronic control unit sends a signal to trigger the gas generator pyrotechnic charges. The combustion of the propellant produces a chemical reaction creating inert gas whose pressure produces a force that thrusts a piston upwards, changing the rotary movement of the reel into the opposite direction of the seat belt, rewinding it by a few centimetres.

Once the pretensioners have been activated, the belts are locked and must be replaced.

Automatic reel with load limiter

The front seat belt reels are located in the side door pillars.

The force limitation is made possible by the use of a torsion bar (2). On the tension side (3), the torsion bar is connected to the reel shaft (1). On the locking side (6), the locking wheel (4) forms one piece with the torsion bar.

If activated, the stop pawl (5) stops the locking wheel. In the case of an impact, the reel shaft, pulled by the seat belt, is made to rotate in the opposite direction to the locking.

The torsion bar has been designed to start turning from the moment a precise traction force is exerted on the seat belt. In this case the seat belt is released as a result. The reel shaft can complete a maximum of 5 revolutions.

Rear side seat belt reels

The rear side seat belt reels are fitted with load limiters like the front ones.

They are located in the side pillars, at the side of the backrest.

Rear centre seat belt reel

The reel for the rear middle seat belt is located inside the rear seat backrest.