Variable Volume Airbag Tether Dynamics
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Solution Overview
Problem
Existing airbags face challenges in managing peak forces on vehicle occupants during collisions, particularly those not wearing seat belts, due to uneven inflation and interaction dynamics.
Innovation Solution
A variable volume airbag with a tether system that initially restricts lateral expansion to prioritize longitudinal inflation, engaging occupants sooner and allowing increased expansion when a threshold force is reached, thereby distributing and dissipating occupant energy more effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the airbag inflates laterally without restriction, then the airbag volume increases and provides more cushioning space, but the lateral expansion delays longitudinal inflation and increases peak forces on occupants
Solution Approach 1:
The tether transitions from a constrained state during initial inflation to an extended state when a threshold force is reached, dynamically adjusting the airbag's lateral expansion characteristics. This dynamic behavior allows the airbag to prioritize longitudinal inflation initially, then permit lateral expansion as needed, resolving the contradiction between volume and peak force.
Solution Approach 2:
The tether pre-constrains the airbag's lateral expansion during the critical initial inflation phase, ensuring that longitudinal inflation occurs first and engages the occupant sooner. This preliminary constraint prevents harmful lateral expansion before the airbag can effectively interact with the occupant, reducing peak forces while maintaining adequate volume.
2Speed
If the tether restricts lateral expansion during initial inflation, then longitudinal inflation is prioritized and engages occupants sooner, but the airbag volume is reduced
Solution Approach 1:
The tether system dynamically adjusts its constraint level based on inflation progress and applied forces. During initial inflation, it maintains strong lateral constraint to prioritize longitudinal expansion and engage occupants sooner. As inflation progresses and forces increase, the tether extends, permitting lateral expansion to restore airbag volume, thus resolving the contradiction between inflation speed and volume.
3Adaptability or versatility
If the tether changes state at a threshold force, then lateral expansion is permitted when needed, but the tether must be designed to withstand and respond to specific force levels
Solution Approach 1:
The tether system utilizes force threshold parameters to trigger state changes in lateral expansion constraint. By designing the tether with specific material properties and geometric configurations, it automatically transitions between constrained and extended states at predetermined force levels, providing adaptive control without complex active systems.
Data Source
AI summary
In at least one implementation, a variable volume airbag includes an inflatable cushion and a tether coupled to the cushion. The inflatable cushion defines an inner volume in which a gas is received to inflate the cushion longitudinally and laterally within a passenger compartment of a vehicle, and has laterally opposed side surfaces defining part of the inner volume of the cushion. The tether is coupled to each of the side surfaces of the cushion and has a first state wherein the tether limits lateral separation of the side surfaces and a second state wherein increased separation of the side surfaces is permitted as compared to the first state.