Impreza F4-2.5L SOHC (2003)
Seat Belt Tensioner: Description and Operation
PRETENSIONER
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 control 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 pulled 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.