Method for controlling an electric belt retractor, and an electric belt retractor

#The invention relates to a method for controlling an electric belt retractor. The invention further relates to an electric belt retractor.

#An electric belt retractor having a belt spool which is coupled to an electric motor and can be driven in the direction of belt retraction and/or belt withdrawal, is part of a vehicle occupant restraint system with which various precautions can be taken on detection of a critical vehicle situation in order to protect a vehicle occupant from negative consequences in the best possible way. The steps taken may comprise, for example, changing the inclination of a back rest of a vehicle seat, closing vehicle windows, pre-tensioning the safety belt and further measures. All these measures are reversible and repeatable; as soon as the vehicle is in a stable state again, the vehicle is returned into its initial state.

#As regards the belt retractor, this means that the safety belt, which was wound up by the electric motor on detection of a critical vehicle situation in order to eliminate the so-called belt slack in the safety belt as largely as possible, is released again as soon as the vehicle state which was detected as being critical is no longer present.

#FIG. 1 shows a diagram with current impulses which occur during the controlling of an electric belt retractor;

#FIG. 2 shows a first embodiment of the belt retractor according to the invention;

#FIG. 3 shows a second embodiment of the belt retractor according to the invention;

#An electric belt retractor for a vehicle occupant restraint system comprises, as described in the introduction, a belt spool which is usually coupled to an electric motor via a reduction gear, and a blocking mechanism with a vehicle-sensitive blocking catch which is able to be guided into undercut blocking teeth.

#In FIG. 1, typical current impulses are shown which occur during the controlling of an electric belt retractor in a critical vehicle state. Firstly, the electric motor is provided with current over a period of time which is necessary for tensioning the belt band (tensioning impulse 10). If a stable vehicle state is then detected, an unlocking impulse 12 occurs in order to release the blocking catch, which may possibly have been guided in, out from the blocking teeth. After this, in addition a coupling release impulse 14 occurs.

#In contrast to known methods, the method according to the invention for controlling an electric belt retractor provides for the detecting of a possible belt band withdrawal during the critical vehicle state. The unlocking impulse 12 only takes place when a belt band withdrawal has been established.