Seatbelt Pretensioner Polymer Rod Gas Venting
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Solution Overview
Problem
Conventional seatbelt pretensioners using metallic balls or rack and pinion systems face issues with weight, cost, low resistance conditions, and the need for complex synchronizing features, as well as challenges in maintaining the locked position and venting gas to prevent overpressure conditions.
Innovation Solution
A seatbelt pretensioning retractor assembly utilizing a polymer rod as a driving element, combined with a seal member featuring a cone-shaped skirt section and a concave head section for enhanced sealing, and a gas generator to produce expanding gas for pretensioning, which helps maintain the locked position and prevent gas leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic balls or rack and pinion systems are used as driving elements, then the pretensioning function is achieved, but the weight and cost increase
Solution Approach 1:
The patent replaces the traditional mechanical driving elements (metallic balls or rack and pinion systems) with a polymer rod as the driving element. This substitution reduces weight while maintaining the pretensioning function through the interaction between the polymer rod and the retractor spool sprocket.
Solution Approach 2:
The patent uses a polymer rod made from composite or engineered polymer materials that provide sufficient strength and stiffness to perform the pretensioning function while being significantly lighter than metallic alternatives. The polymer material allows weight reduction without sacrificing functional reliability.
2Reliability
If metallic balls or rack and pinion systems are used, then the pretensioning function is achieved, but the manufacturing cost increases
Solution Approach 1:
The polymer rod replaces complex mechanical systems (multiple metallic balls with strict tolerances or rack and pinion mechanisms), simplifying the manufacturing process. The polymer rod can be manufactured as a single integrated component through molding processes, eliminating the need for assembling multiple precision metal parts.
Solution Approach 2:
The polymer rod provides a cost-effective alternative to expensive metallic components. While the rod may have a limited service life, its low manufacturing cost and simplicity make it economically advantageous compared to precision-machined metal parts with strict tolerances.
3Reliability
If a series of metallic balls are used as driving elements, then the pretensioning function is achieved, but the device complexity increases due to the need for synchronizing or clutch features
Solution Approach 1:
The patent extracts and eliminates the complex synchronizing or clutch features required by metallic ball systems. The polymer rod directly engages the retractor spool sprocket without requiring intermediate synchronizing mechanisms, simplifying the overall device architecture.
Solution Approach 2:
The polymer rod serves multiple functions: it acts as the driving element, provides structural support, and enables direct engagement with the sprocket. This multi-functionality eliminates the need for separate synchronizing or clutch components, reducing device complexity.
4Reliability
If the gas pressure is maintained beyond the amount needed for the pretensioning stroke, then the locked position is maintained, but the weight and cost increase
Solution Approach 1:
The patent employs a dynamic locking mechanism where the polymer rod and retractor spool sprocket engage to maintain the locked position after pretensioning. This mechanical locking system eliminates the need for continuous gas pressure maintenance, allowing the gas generator to be smaller and lighter while still achieving reliable position maintenance.
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 solution reduces weight and cost, improves sealing efficiency, and effectively maintains the locked position of the seatbelt, while also addressing low-resistance and overpressure conditions through enhanced sealing and venting mechanisms.
Implementation Method 1
A tube has an arcuate and curved shape having a first end for fluid communication with a gas generator and a second end in fluid communication with the interior cavity of the housing... A driving element includes a polymer rod that is configured to extend in a longitudinal direction. The polymer rod is disposed within the tube and is translatable through the tube in a first direction towards the sprocket in response to an actuation by the gas generator.
Implementation Method 2
A seal member is disposed between the gas generator and the stopper, and the seal member includes a skirt section in a proximal end of the seal member and a head section in a distal end of the seal member... the skirt wall is expanded due to expanding gas produced from the gas generator so that the seal member is deformed as a cylindrical shape along a whole length of the seal member.
Data Source
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AI summary
A seatbelt pretensioning retractor assembly for use in a vehicle is provided. The pretensioning assembly includes a tube in fluid communication with a gas generator and a driving element disposed therein that travels in a first direction in response to actuation of the gas generator. The driving element includes a polymer rod. A stopper is coupled to an end portion of the polymer rod. In one example, a seal member disposed between the gas generator and the stopper includes a head section and a skirt section. In another example, the tube has an opening that is adjacent to an exit to facilitate venting gas from the gas generator.