GF91.40-P-4000-03Q Front Emergency Tensioning Retractor, Function

GF91.40-P-4000-03Q Front Emergency Tensioning Retractor, Function

Triggering of the 3 emergency tensioning retractor unit ignition stages
If a frontal or rear end collision occurs, from a certain deceleration or acceleration the restraint systems control unit (N2/7) issues the electrical pulse for triggering the driver ETR ignition squib (R12/1) or the front passenger ETR squib (R12/2).

After the initial triggering, depending on when full belt tensioning occurs, the second and third ignition stages are triggered. The figure below shows the functional sequence of an emergency tensioning retractor actuation.

Belt force limiter
The ETR is equipped with a force limiter that reduces the force of the belt on the occupant's body after belt tensioning has occurred, without adversely affecting the protective effect of the be

Electromechanical locking system
In a further crash, the normal protective function of the belt is retained. The retractor axle of the locking system is then blocked without any retraction or force limitation thereby assuming the full load.

Function
When the solenoid is actuated, a magnetic field is created. This repels the permanent magnet with the locking lever. The locking lever engages in the toothing of the clutch disk and blocks the ETR reel shaft.

Component Identification:

^ The ignition squib (a) is ignited by the ETR control unit (N2/7).
^ The gas produced by the ignition creates gas pressure and causes the piston to rotate (b). It causes the seat belt to tighten.
^ 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 pylon (c).
^ The gas pressure moves the piston (b) further and causes the belt to be tensioned further.
^ The gas pressure transports the 2nd ignition pylon (e) in the direction of the 2nd ignition cartridge (f).
^ The ignition cartridge (f) is mechanically ignited by the 2nd ignition pylon (e).
^ The gas pressure moves the piston (b) into the end state. The red pin is visible.

Component Identification:

Recognition of deployment
When all 3 ignition stages have taken place, this is indicated by a red pin (arrow) that protrudes from the ETR housing (1).

If all 3 ignition stages did not take place when an accident occurred the unit must be disposed of accordingly. In Germany disposal is possible through the Mercedes-Benz Recycling System "MeRSy". The corresponding legal requirements should be observed in all other countries. Emergency tensioning retractor units in which the red pin projects, can be disposed of in the normal way.