Steering Column Energy Absorption Strap Tuning
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Solution Overview
Problem
Vehicle OEMs face challenges in tuning the energy absorption characteristics of steering column assemblies, particularly in controlling initial breakaway loads, delayed energy absorption zones, and transitioning to final running load zones, especially when these requirements are stringent and need to be consistent across both power and manual steering columns.
Innovation Solution
The proposed steering column assembly incorporates an energy absorbing strap assembly with a single, integrally formed strap and a connecting structure with a shear pin, allowing for adjustable energy absorption profiles by controlling initial breakaway and activating running loads through mechanical fasteners and interaction features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple separate components are used to achieve customizable energy absorption characteristics, then the ability to tune crash stroke energy absorption load, initial breakaway, and load profile duration is improved, but the device complexity increases
Solution Approach 1:
The energy absorbing strap is segmented into multiple leg portions (first leg portion, second leg portion, third leg portion) that can be independently configured with different interaction features. This segmentation allows each portion to contribute differently to the energy absorption profile, enabling customization of crash stroke load, initial breakaway, and load profile duration while maintaining a relatively simple overall structure.
Solution Approach 2:
Different leg portions of the energy absorbing strap are equipped with different interaction features (protrusions, slots, mechanical fasteners) at specific locations. This local differentiation allows each portion to engage with the jacket at different stages of collapse, creating the desired load profile with initial breakaway followed by delayed energy absorption and final running load zones without requiring completely separate components.
2Device complexity
If a single integrally formed strap structure is used, then the device complexity is reduced, but the ability to control initial breakaway and delayed energy absorption zones is limited
Solution Approach 1:
While the strap is integrally formed as a single piece, it is functionally segmented into multiple leg portions with distinct interaction features. The first leg portion engages early in the collapse sequence, the second leg portion provides delayed engagement, and the third leg portion contributes to the final running load zone. This functional segmentation within an integral structure enables precise control over the energy absorption profile.
Solution Approach 2:
The interaction features (protrusions, slots, mechanical fasteners) are designed to engage and disengage dynamically during the collapse sequence. This allows the strap to transition between different load states (initial breakaway, delayed energy absorption, final running load) in a controlled manner, providing adaptability despite the integral structure.
3Adaptability or versatility
If mechanical fasteners are used to resist relative movement up to a predetermined load, then the initial breakaway load control is improved, but the component complexity increases
Solution Approach 1:
The mechanical fasteners are integrated directly into the energy absorbing strap structure itself, rather than being separate components. The fasteners are formed as part of the strap's leg portions and work in conjunction with slots in the jacket to provide controlled engagement and disengagement. This merging reduces overall component complexity while maintaining precise initial breakaway load control.
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 over energy absorption characteristics, allowing for a wide range of initial peak loads followed by delayed energy absorption and final running loads, thus meeting the stringent requirements of OEMs while reducing component complexity.
Implementation Method 1
a shear pin extending through the first leg portion and the second leg portion
Implementation Method 2
an energy absorbing strap having a first leg portion, a second leg portion and a curved portion connecting the first leg portion and the second leg portion
Data Source
AI summary
A steering column assembly includes a lower jacket. The steering column assembly also includes an upper jacket in telescoping engagement with the lower jacket. The steering column assembly further includes an energy absorbing strap having a first leg portion, a second leg portion and a curved portion connecting the first leg portion and the second leg portion, the first leg portion coupled to the upper jacket, wherein the first leg portion, the second leg portion and the curved portion define a single integrally formed structure. The steering column assembly yet further includes a protrusion extending from the energy absorbing strap and disposed within a slot defined by the upper jacket.