Variable-Length Tether for Roof Rail Airbag Stiffness
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Solution Overview
Problem
Roof rail airbags face challenges in achieving sufficient stiffness to contain occupants without external backing barriers, especially in vehicles with large window openings, due to compromises in tether placement that affect deployment kinematics and stiffness.
Innovation Solution
A variable-length tether system that couples the front edge of the roof rail airbag to the A-pillar, with features like spools and tensioning mechanisms to remove slack and maximize stiffness during deployment, ensuring the tether remains taught and effectively contains occupants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fixed-length tether is used to attach the airbag to the vehicle body, then the tether may interfere with deployment kinematics or fail to provide sufficient stiffness, but a variable-length tether system increases device complexity
Solution Approach 1:
The tether system transitions from a fixed-length design to a variable-length design using spools and tensioning mechanisms. The spools allow the tether length to dynamically adjust during deployment, enabling the tether to remain taught and provide maximum stiffness while accommodating the changing spatial relationship between the airbag and vehicle body during deployment.
Solution Approach 2:
Spools are introduced as intermediary components between the tether and the vehicle body structure. These spools act as mediators that manage the tether length variation, allowing the tether to maintain tension throughout deployment while the airbag expands. The spools convert the complex variable-length requirement into a simple rotational mechanism.
2Ease of operation
If the tether is made longer to avoid interfering with deployment, then deployment kinematics improve, but the tether becomes slack and loses stiffness
Solution Approach 1:
The tether length is made dynamic through the spool mechanism, allowing it to extend during deployment to avoid interference with airbag expansion, then maintain tension through the tensioning mechanism. This dynamic adjustment enables the tether to be long enough during deployment while remaining stiff through active tension management.
Solution Approach 2:
The system changes the length parameter of the tether dynamically during deployment. The spool mechanism allows the tether length to increase as the airbag deploys, preventing interference with deployment kinematics, while the tensioning mechanism ensures the tether remains taught and stiff throughout the process.
3Strength
If the tether is made shorter to maintain stiffness, then tether tension is maintained, but the tether interferes with airbag deployment
Solution Approach 1:
The tether length is dynamically adjusted during deployment. Initially, the tether is shorter to maintain stiffness and tension, but as the airbag deploys, the spool mechanism allows the tether to extend, preventing interference with the deployment process. This dynamic adjustment resolves the conflict between maintaining tension and avoiding interference.
Solution Approach 2:
The tether is pre-configured with a specific initial length that provides sufficient stiffness for containing occupants. The spool mechanism is pre-positioned to allow the tether to extend only after deployment has begun, ensuring that the tether maintains its stiff, tensioned state during the critical containment phase while still allowing deployment to proceed.
Data Source
AI summary
An airbag assembly according to the present disclosure includes an airbag cushion and a first tether. The airbag cushion is configured to be stored in a roof of a vehicle when the airbag cushion is uninflated. The airbag cushion is configured to at least partially cover an opening in a sidewall of the vehicle when the airbag cushion is inflated. The first tether is coupled to a forward edge of the airbag cushion at a first location. The first tether is configured to be coupled to a body of the vehicle at a second location. A length of the first tether between the first and second locations is configured to vary as the airbag cushion is deployed.