Pic. 8.52. Pretensioner
Pretensioner operation
In a frontal impact at a certain angle, in the event of a vehicle collision, the gas generator control circuit in the SRS electronic control unit is closed, which ignites the gas generator electric igniter.
The gas produced by the gas generator causes the piston to move in the intake manifold housing of the pretensioner (cylinder), which acts on the ratchet (rack gear).
The ratchet drives the piston gear and the drive gear drives the planetary gears (planet gears).
Finally, the seatbelt is retracted (stretched) rotation of the inertial coil. Thus, the seat belt pretensioner helps to reduce the likelihood of injury to the driver (or front passenger) by tightening his seat belt. This prevents the driver from moving (or front passenger) forward and hit the steering wheel or instrument panel in a vehicle collision.