Steering Column Shroud Breakaway Interface for Controlled Collapse
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Solution Overview
Problem
Existing collapsible steering column assemblies face challenges in providing a compact design with controlled breakaway load, avoiding mid-collapse load spikes, and requiring complex brackets for shroud support during secondary impacts.
Innovation Solution
A collapsible steering column assembly with a shroud that includes a slot and fastener system allowing the shroud to break away upon exceeding a threshold load, utilizing a connection member with energy absorption segments and biasing members to control the breakaway load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the shroud attachment point is fixed during steering column collapse, then the shroud can be supported without complex brackets, but a method to separate the shroud from the fixed attachment point is needed during secondary impact
Solution Approach 1:
The shroud attachment system transitions from a static fixed connection to a dynamic system that can change state based on load conditions. The breakaway fastener mechanism allows the attachment to remain fixed during normal operation but automatically separate when the steering column experiences secondary impact forces, thus supporting the shroud without complex brackets while maintaining separation capability when needed.
Solution Approach 2:
The attachment system utilizes load threshold parameter changes to trigger separation. The breakaway fastener is designed with a specific load threshold that, when exceeded during secondary impact, causes the fastener to separate the shroud from the steering column. This allows the same attachment point to serve both as a fixed support during normal use and as a separable connection during impact events.
2Reliability
If a breakaway plastic boss is used on the column tube, then the shroud can separate during impact, but it results in a load spike midway during column collapse
Solution Approach 1:
The breakaway fastener acts as an intermediary mechanism between the shroud and the steering column. Instead of using a plastic boss that breaks away abruptly causing load spikes, the fastener provides a controlled separation mechanism that distributes the separation force over time, eliminating the mid-collapse load spike while still enabling shroud separation during secondary impact.
3Strength
If the shroud attachment is positioned further away from the steering wheel, then the shroud is better supported, but it requires lengthy and complex brackets that limit collapse stroke
Solution Approach 1:
The shroud attachment is merged with the steering column assembly structure itself, eliminating the need for separate lengthy brackets. The breakaway fastener integrates the attachment function directly into the column assembly, providing adequate shroud support while maintaining a compact design that does not limit the collapse stroke.
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 assembly effectively absorbs energy by allowing the shroud to separate from the steering column assembly during high loads, preventing mid-collapse load spikes and maintaining a compact design without complex brackets.
Implementation Method 1
a biasing member, such as a spring, configured to apply a force to the fastener
Implementation Method 2
upon an impact exceeding a threshold load, at least a portion of the fastener is permitted to slide out of the slot through the opening
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A portion of a shroud (30) is adapted to be secured to a steering column assembly (10). The portion of the shroud (30) includes a slot (46) for receiving a portion of a fastener (36) and an opening (48) of sufficient size that at least a portion of the fastener (36) is permitted to fit through to allow the shroud (30) to break away from the steering column assembly (10) upon an impact exceeding a threshold load. The shroud (30) is fastened to the steering column assembly (10) via a fastener (36) and a connection member that is joined to the column tube.