Method for operating a belt retractor and a belt retractor for a safety belt

Abstract

In a method for operating a belt retractor, the belt retractor comprising a belt tensioner drive and with a pre-tensioner drive which can both exert a torque onto a belt spool in a direction for winding a safety belt, the pre-tensioner drive is prevented from exerting a torque onto the belt spool through the activation of the belt tensioner drive. In a belt retractor for a safety belt, having a belt spool, a pre-tensioner drive with a drive motor, which can turn the belt spool in the winding direction for the purpose of pre-tensioning the safety belt, and with a belt tensioner drive which can drive the belt spool for the purpose of a belt tensioning, a safety mechanism is provided, which through an activation of the belt tensioner drive prevents the pre-tensioner drive from driving the belt spool in the winding direction.

Description

[0001] The invention relates to a method for operating a belt retractor. BACKGROUND OF THE INVENTION [0002] The invention in particular relates to a belt retractor which is provided with a belt tensioner drive and with a pre-tensioner drive, which can both exert a torque onto a belt spool in a direction for winding the safety belt. The invention additionally relates to a belt retractor for a safety belt, with a belt spool, a pre-tensioner drive with a drive motor which can rotate the belt spool for the purpose of pre-tensioning the safety belt in the winding direction, and with a belt tensioner drive which can drive the belt spool for the purpose of a belt tensioning. [0003] Both the pre-tensioner drive and also the belt tensioner drive basically serve to drive the belt spool in the winding direction when a vehicle state exists which is classified as critical, so that the so-called belt slack of the safety belt is eliminated and the safety belt lies taut against the body of a vehicl...

AI Technical Summary

Benefits of technology

[0007] In order to solve this problem, the invention provides a method in which, when the belt tensioner drive is activated, through the activation of the belt tensioner drive the pre-tensioner drive is prevented from exerting a torque on the belt spool. A belt retractor according to the invention is distinguished in that a safety mechanism is provided, which with an activation of the belt tensioner drive prevents the pre-tensioner drive from driving the belt spool in the winding direction. In this way, it is ensured that the force level provided by the force-limiter system is not “falsified” by the pre-tensioner drive; irrespective of whether the pre-tensioner drive has been activated or not, the pre-tensioner drive does not have to be carried along in the unwinding direction of the safety belt, when after activation of the belt tensioner drive a high force is acting in the safety belt, which leads to the response of the force-limiter system.

[0008] According to a preferred embodiment of the invention, through the activation of the belt tensioner drive the flux of force from the pre-tensioner drive to the belt spool is interrupted. In this way, the belt spool can turn freely from the pre-tensioner drive in the unwinding direction when the force-limiter system responds. The pre-tensioner drive does not need to be carried along.

[0009] According to a further preferred embodiment of the invention, provision is made that the pre-tensioner drive has an electric motor and that through the activation of the belt tensioner drive the current supply of the electric motor is interrupted. This prevents the electric motor from acting on the belt spool in the winding direction if the belt spool were to in fact rotate in the opposite direction under the action of the force effective in the safety belt, i.e. in the unwinding direction, in order to realize a force-limiting function. Then only the electric motor has to be carried along; the torque occurring here is, however, comparatively small, so that the force defined by the force-limiter system in the safety belt is not substantially increased.

[0010] According to a further embodiment of the invention, provision is made that the pre-tensioner drive has an electric motor and that through the activation of the belt tensioner drive, the electric motor is operated in a direction for unwinding of the safety belt. In this state, the electric motor therefore assists the unwinding of the safety belt from the belt spool and hence the response of the force-limiter system. As the torque provided by the electric motor is comparatively small, a negligible effect is produced on the force level provided by the force-limiter system, from which the force-limiting function is realized.

[0011] According to the invention, provision is made that the belt tensioner drive has a pyrotechnic gas generator which through its activation prevents the pre-tensioner drive from exerting a torque on the belt spool. This has the advantage that no external additional control is necessary in order to uncouple the pre-tensioner drive from the belt spool or to reverse its direction of rotation; the uncoupling or reversal of the direction of rotation of the pre-tensioner drive can be achieved with the gas pressure which is provided by the belt tensioner drive for the purpose of the belt tensioning.

Problems solved by technology

Then only the electric motor has to be carried along; the torque occurring here is, however, comparatively small, so that the force defined by the force-limiter system in the safety belt is not substantially increased.

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