Seat Belt Retractor Decoupling for Controlled Force-Limited Extension
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Solution Overview
Problem
Existing belt retractors experience uncontrolled further extension of the belt webbing after reaching the end of the second stage of force-limited extension, leading to potential damage and loss of control.
Innovation Solution
A belt retractor with an actively triggerable decoupling device that allows the belt shaft to be uncoupled from the first force-limiting device, enabling controlled further extension through a second force-limiting mechanism, utilizing a pyrotechnic gas generator or electromagnet to rapidly decouple the belt shaft and switch between force-limited stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the first force-limiting device provides two-stage force limitation, then energy absorption is distributed across two stages, but the device complexity increases
Solution Approach 1:
The first force-limiting device is designed to perform multiple functions: it provides both first-stage and second-stage force limitation, and also serves as a coupling point for the decoupling device. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing complexity while achieving energy distribution across stages
2Reliability
If a decoupling device is added to prevent uncontrolled extension, then reliability is improved, but the device complexity increases
Solution Approach 1:
The decoupling device is integrated with the existing force-limiting device structure. The coupling element of the decoupling device is combined with the housing and force-limiting device components, merging multiple functions into a unified structure rather than adding completely separate mechanisms, thus reducing overall complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents damage by allowing controlled belt winding movement after reaching the end of the first force-limited extension, providing a three-stage force-limited belt webbing extension with reduced energy absorption by the first force-limiting device, ensuring safe and controlled operation.
Implementation Method 1
utilizing a pyrotechnic gas generator or electromagnet to rapidly decouple the belt shaft
Implementation Method 2
utilizing a pyrotechnic gas generator or electromagnet to rapidly decouple the belt shaft
Data Source
AI summary
The invention relates to a belt retractor for a seat belt of a motor vehicle, comprising a belt shaft which is rotatably mounted in a housing frame, a profiled head which can be locked relative to the housing frame, and a force-limiting device, wherein the force-limiting device is coupled on the one hand to the profiled head and on the other hand to the belt shaft and wherein the force-limiting device allows a force-limited rotation of the belt shaft relative to the locked profiled head, characterized by an actively releasable decoupling device.