Subaru 2002 Impreza Service Manual page 399

SEAT BELT
Seat Belt System
D: PRETENSIONER
1. CONSTRUCTION
The driver's and front passenger's seat belts are equipped with seat belt pretensioners.
The pretensioners use the front sub sensors and the airbag control module inside sensors to con-
trol their operation. If the sensors detect an impact exceeding the predetermined level during a
frontal or front-angled collision, the front seat belts are quickly rewound by the retractors to take
up slacks for maximum restraining of the seat occupants. If the load placed on a seat belt exceeds
the predetermined level, the torsion bar twists to allow the belt to be payed out, thus lessening the
load imposed on the belt wearer's chest. Once the seat belt pretensioner has been activated, the
seat belt retractor remains locked.
Driver's pretensioner
The gas generator is activated.
The generated gas pushes the steel balls.
Moving steel balls cause the ring gear to rotate.
(1)
Tube
(2) Ring gear
(3) Pinion
(4) Steel ball
(5) Spring
(6) Gas generator
(7) Torsion bar
NF0481
SB-5