Front emergency tensioning retractor, function - GF91.40-P-4000-03T
Triggering the three ignition stages of the emergency tensioning retractor unit
In the event of a crash (frontal or rear end collision) and, as of a specific deceleration or acceleration, the restraint systems control unit (N2/7) sends an electrical pulse to trigger the emergency tensioning retractor to the driver emergency tensioning retractor squib (R12/1) or front passenger emergency tensioning retractor squib (R12/2).
After this, depending on when complete belt tensioning occurs, the 2nd and, if necessary, the 3rd. ignition stage are activated. The figure below shows the functional sequence of an emergency tensioning retractor actuation.
Belt force limiter
The emergency tensioning retractor unit is equipped with a belt force limiter, which in the event of emergency tensioning during a crash reduces loads exerted on occupant bodies using the front passenger belt force limiter (R12/26) and the driver belt force limiter (R12/27), without impairing the protective capability of the belt.
In a further crash, the normal protective function of the belt is retained. Without tensioning and force limiting, the inertia reel shaft is then blocked by the locking system and absorbs the complete load.
Emergency tensioning retractor functional sequence
- The squib (a) is triggered by the airbag control unit.
- The combustion gas produced by ignition, generates a gas pressure and thus causes the piston to rotate (b), whereupon the belt is tensioned.
- The gas pressure then transports the 1st ignition pylon (c) towards the 1st ignition cartridge (d).
- The ignition cartridge (d) is mechanically ignited by the ignition cap (c).
- The gas pressure moves the piston (b) further and causes the belt to be tensioned further.
- The gas pressure transports the 2nd ignition cap (e) in the direction of the 2nd ignition cartridge (f).
- The 2nd ignition cartridge (f) is ignited.
- The gas pressure moves the piston (b) into the end state. The red pin is visible.
Recognition of deployment
Ignition of all the ignition stages is indicated by a red pin (arrow) projecting from the housing of the emergency tensioning retractor unit (1).