Adaptive Load Limiting Seat Belt Retract
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Solution Overview
Problem
Current seat belt retractors face challenges in reducing costs, complexity, and packaging size while providing adaptive load limiting characteristics, as they often require additional pyrotechnic activation components and complex systems to select between high and low load limiting conditions.
Innovation Solution
An adaptive load limiting seat belt retractor featuring a roto-type pretensioner activated by a micropyrotechnic gas generator, coupled with high and low load limiting torsion bars, which selects between load limiting characteristics without additional pyrotechnic components, allowing for dual load limiting within the same packaging envelope as standard retractors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional pyrotechnic activation components and complex control systems are added to select between high and low load limiting conditions, then adaptive load limiting performance is improved, but device complexity and cost increase
Solution Approach 1:
The single pyrotechnic activation device is designed to perform multiple functions: it can activate the pretensioner mechanism and simultaneously select between high and low load limiting characteristics through the position-dependent firing mechanism. This eliminates the need for separate components for pretensioning and load limiting selection, resolving the contradiction between adaptability and device complexity
Solution Approach 2:
The patent combines the pretensioner activation function and load limiting selection function into a single integrated pyrotechnic device. The firing pin mechanism merges the activation trigger with the selection logic, where the firing position automatically determines the load limiting characteristic without requiring additional control electronics or components
2Adaptability or versatility
If additional pyrotechnic activation components and control systems are added to select between high and low load limiting conditions, then adaptive load limiting performance is improved, but cost increases
Solution Approach 1:
The single pyrotechnic activation device performs multiple functions including pretensioner activation and load limiting selection, eliminating the need for separate components and reducing overall system cost while maintaining adaptive performance capability
Solution Approach 2:
The patent extracts the control logic from complex electronic systems and embeds it directly into the mechanical firing mechanism structure. The selection of load limiting characteristics is determined by the physical position of the firing pin, eliminating the need for expensive control electronics, sensors, and associated software
3Volume of stationary object
If the retractor is designed to fit within the same packaging envelope as standard retractors, then packaging efficiency is improved, but device complexity increases
Solution Approach 1:
The patent employs a nested arrangement where the high and low load limiting torsion bars are concentrically positioned within each other. The low load limiting torsion bar is nested inside the high load limiting torsion bar, allowing both mechanisms to occupy the same spatial envelope as a standard retractor while providing dual load limiting functionality
Solution Approach 2:
The patent transitions from a planar or linear arrangement of components to a three-dimensional concentric configuration. By stacking the torsion bars in the radial dimension, the design accommodates dual load limiting mechanisms within the same external dimensions, resolving the contradiction between packaging efficiency and device 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
This solution reduces costs and complexity by eliminating the need for separate pyrotechnic activation devices, enabling dual load limiting without increasing component count, while maintaining packaging efficiency and enhancing restraint performance.
Implementation Method 1
A roto-type pretensioner activated by firing a micropyrotechnic gas generator
Implementation Method 2
a torsion bar coupled between the webbing spool and the inertial locking device which provides controlled torsional deflection in response to belt webbing loads
Data Source
AI summary
An adaptive load limiting seat belt retractor particularly adapted for motor vehicle applications. The retractor provides multiple levels of load limiting through the use of a pair of internal torsion bar elements. The torsion bar elements control the tension force on the seat belt webbing during an impact in a manner which provides desirable crash management characteristics. The retractor can be switched between high and low load limiting modes through activation of a pyrotechnic pretensioner. When the pyrotechnic pretensioner is not activated, the retractor provides a low load level characteristic. Pretensioner activation switches the retractor into a high load level operating condition. A high load limiting level is provided when the pretensioner is not activated if the spindle rotation exceeds a limited level in the low load limiting condition. A degressive load limiting feature may be provided to cause load limiting to begin at a higher level than the high load limiting level, and then step down the high load limiting level.