Spiral Turn Limiter for Load Limiting Seat Belt Retractor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current seat belt retractors with torsion bar load limiters face challenges in limiting total rotational deflection and achieving complex load limiting profiles, leading to increased complexity, cost, and packaging size issues, while also requiring adaptability for specific vehicle applications with a low part count.
Innovation Solution
The integration of a helical or spiral cam mechanism within the seat belt retractor to limit relative rotation between components, allowing for progressive and digressive load limiting capabilities by controlling the movement of a ball element along a helical or spiral flight, thereby restricting torsional deflection and tailoring load limiting characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-stage torsion bar system is used to provide multilevel load limiting capabilities, then load limiting characteristics can be tailored, but device complexity and packaging size increase
Solution Approach 1:
The torsion bar is divided into multiple stages with different torsional stiffness characteristics. Each stage provides a different load limiting level, allowing the system to achieve multilevel load limiting capabilities through the segmented structure rather than requiring multiple separate torsion bars or complex mechanisms.
Solution Approach 2:
The multi-stage torsion bar system nests multiple functional stages within a single integrated torsion bar structure. The different stages are arranged concentrically or sequentially within the same component envelope, reducing packaging size while maintaining the ability to provide multiple load limiting levels.
2Manufacturing precision
If sophisticated digressive and progressive load limiting profile systems are developed, then load limiting characteristics can be accurately tailored, but device complexity and cost increase
Solution Approach 1:
Different sections of the torsion bar are designed with locally optimized properties to achieve digressive or progressive load limiting profiles. The torsional stiffness varies along the length or cross-section of the bar, allowing precise control of the load limiting characteristics without requiring complex external control systems.
Solution Approach 2:
The torsional stiffness parameter of the torsion bar is varied along its structure to create digressive or progressive load limiting profiles. By changing the geometric parameters (such as cross-sectional area, moment of inertia) or material properties at different locations, the system achieves accurate load limiting characteristics.
3Ease of operation
If mechanisms are added to limit total rotational deflection of the torsion bar, then multiple turns of relative rotation can be controlled, but device complexity increases
Solution Approach 1:
The rotational deflection limiting function is merged with the load limiting function in a single integrated mechanism. The cam structure simultaneously controls the rotational deflection of the torsion bar and regulates the load limiting force, eliminating the need for separate limiting mechanisms and reducing overall system complexity.
Solution Approach 2:
A cam mechanism serves as an intermediary element between the torsion bar and the webbing payout system. The cam profile translates the rotational deflection of the torsion bar into controlled webbing payout, limiting the total rotation while providing the desired load limiting characteristics.
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 enables precise control of load limiting forces, reduces complexity and cost, and allows for easy adaptation to different vehicle applications by limiting rotational deflection and providing multiple turns of relative rotation, enhancing the overall performance of seat belt retractors.
Implementation Method 1
The bar section between the attachment points undergoes elastic and plastic torsional deflection, enabling torsion controlled relative rotation between the spool and the retractor frame
Implementation Method 2
The bar section between the attachment points undergoes elastic and plastic torsional deflection
Implementation Method 3
Several embodiments are described, each having a form of a helical or spiral cam which limits relative rotation between components of the retractors
Data Source
AI summary
A motor vehicle seat belt retractor having load limiting features for controlling seat belt restraint loads for a retractor having a spool for storing belt webbing and rotatable with respect to a retractor frame, and a locking mechanism for locking the spool to provide vehicle occupant restraint. A load limiting element coupled with the spool limits restraint loading of the seat belt webbing upon locking of the spool. A rotational displacement limiting mechanism limits the displacement of the load limiting element, the limiting mechanism having a cam forming a spiral flight rotatable with the load limiting element and a cam follower engaging the spiral flight. The cam and the cam follower interengage to reach an end position preventing further relative angular displacement beyond a predetermined angular displacement of the load limiting element. Embodiments provide various configurations for the cam and cam follower elements.