Seatbelt Retractor Torsion Bar With Staged Webbing Payout
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Solution Overview
Problem
Current seatbelt load-limiting features do not effectively manage the varying loads exerted on occupants of different sizes during a vehicle impact, as the load-limiting threshold is not adequately adjustable to accommodate different occupant sizes, potentially leading to inadequate chest compression reduction for larger occupants.
Innovation Solution
A seatbelt retractor design incorporating a torsion bar with a weaker connection at its second end, featuring a wire and rod with distinct failure points, allows controlled payout of webbing by disconnecting at specific rotational thresholds, providing additional extension to mitigate load on the occupant's chest during impacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed load-limiting threshold is used in the seatbelt retractor, then the device structure is simple, but it cannot effectively manage varying loads for occupants of different sizes
Solution Approach 1:
The patent changes the load-limiting parameter dynamically by using a torsion bar mechanism with controlled failure points. The torsion bar rotates to different angular positions based on the applied load, and the wire disconnects at specific rotational thresholds, thereby adjusting the effective load-limiting threshold according to the occupant's size and the force exerted during impact.
Solution Approach 2:
The patent introduces dynamic behavior to the load-limiting mechanism by allowing the torsion bar to rotate and the wire connection to fail at predetermined rotational positions. This dynamic system adapts the load-limiting threshold during the impact event based on the magnitude and duration of the applied force, rather than using a static fixed threshold.
2Reliability
If the load-limiting threshold is set to accommodate larger occupants, then safety for large occupants is improved, but chest compression may be excessive for smaller occupants
Solution Approach 1:
The torsion bar mechanism enables the load-limiting threshold to change parameters dynamically during impact. For larger occupants exerting higher forces, the torsion bar rotates further before wire disconnection, allowing greater webbing payout and reducing chest compression. For smaller occupants with lower forces, the wire disconnects at smaller rotation angles, maintaining higher load-limiting thresholds to prevent excessive chest compression.
Solution Approach 2:
The patent applies different load-limiting characteristics to different phases of the impact event through the torsion bar's rotational progression. The first cap provides initial resistance, the torsion bar provides progressive resistance with rotation, and the wire connection provides final disconnection at a predetermined angle. This creates localized quality variations in the load-limiting response based on the severity and duration of the impact force.
3Adaptability or versatility
If the wire connection at the second end is made weaker, then controlled payout is achieved at specific rotational thresholds, but the connection strength is reduced
Solution Approach 1:
The patent deliberately changes the strength parameter of the wire connection at the second end to be weaker than the connection at the first end. This parameter change enables the wire to fail at a predetermined rotational threshold of the torsion bar, providing controlled payout capability. The weakened connection is strategically designed to fail at a specific point in the torsion bar's rotation, allowing the mechanism to transition from a locked state to a payout state at the appropriate moment during impact.
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 design ensures controlled webbing payout to manage occupant loads, reducing chest compression across a range of occupant sizes by strategically failing at defined rotational thresholds, thus enhancing safety during vehicle impacts.
Implementation Method 1
a torsion bar having a first end fixed to the first end of the spool and a second end operatively engaged with the housing. The torsion bar includes a wire elongated along the axis and connected to the first end of the torsion bar and the second end of the torsion bar
Data Source
AI summary
A seatbelt retractor comprises a housing having a first end and a second end. The seatbelt retractor includes a spool having a first end and a second end each rotatably supported by the housing, the spool being elongated on an axis from the first end to the second end. The seatbelt retractor includes a torsion bar having a first end fixed to the first end of the spool and a second end operatively engaged with the housing. The torsion bar includes a wire elongated along the axis and connected to the first end of the torsion bar and the second end of the torsion bar.