Progressive Load Seatbelt Retractor for Occupant Energy Management
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Solution Overview
Problem
Conventional seatbelt retractors with torsion bars provide limited energy management, primarily focusing on single-level load absorption, which is inadequate for the new NCAP criteria that emphasizes chest deflection and compression during dynamic vehicle events, failing to effectively restrain occupants of varying sizes.
Innovation Solution
A seatbelt retractor design featuring a spool assembly with a torsion spring energy absorbing member that provides progressive load resistance, transitioning from a lower to higher energy absorption as the occupant displaces, allowing for efficient energy management across a range of occupant sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single level load limiter (torsion bar) is used, then the acceleration of the occupant is limited, but the chest deflection and compression are not effectively controlled for occupants of varying sizes
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a static, single-level load limiter to a dynamic, progressive load limiting system. The retractor includes multiple energy absorbing members (first and second energy absorbing members) that engage at different load levels, allowing the system to adapt its resistance characteristics based on the magnitude of the applied force. This enables effective restraint for occupants of varying sizes while maintaining reliability in limiting chest deflection and compression.
Solution Approach 2:
The patent implements parameter changes by varying the load resistance parameters across different stages of deployment. The first energy absorbing member provides initial load resistance at a first load level, while the second energy absorbing member engages to provide additional resistance at a second, higher load level. This staged parameter change allows the system to effectively address the needs of occupants of different sizes and severities of impact.
2Adaptability or versatility
If a progressive load resistance mechanism is implemented, then energy management is improved for varying occupant sizes, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the load limiting function into distinct segments or stages. The retractor system is divided into multiple energy absorbing members, each responsible for a specific load level. The first energy absorbing member handles lower load conditions, while the second energy absorbing member handles higher load conditions. This segmentation allows the complex function of progressive load limiting to be achieved through modular, manageable components.
Solution Approach 2:
The patent implements the nested doll principle by arranging energy absorbing members in a nested configuration where the second energy absorbing member is positioned within or alongside the first energy absorbing member's structure. This nested arrangement allows multiple functions to be integrated in a compact space, reducing the overall device complexity while maintaining the progressive load resistance capability.
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
The progressive load and energy absorption mechanism effectively limits chest deflection and compression of occupants, providing improved performance for both small and large occupants by tailoring energy management to the specific needs of each, aligning with the updated NCAP criteria.
Implementation Method 1
an energy absorbing member having a first end operatively connected to the locking base and a second end operatively connected to the spool; wherein the energy absorbing member provides a progressive level of load resistance upon relative rotation between the spool and the locking base
Implementation Method 2
a torsion bar configured to transfer torque between the spool and the operatively coupled locking base and case
Implementation Method 3
The torsion bar 1060 is generally made from steel to provide a constant load throughout their design range
Data Source
AI summary
A retractor assembly comprising a spool configured to wind and unwind the webbing, a lock base, and an energy absorbing member having a first end operatively connected to the locking base and a second end operatively connected to the spool. The energy absorbing member provides a progressive level of load resistance upon relative rotation between the spool and the locking base.