Seatbelt Pretensioner Assembly with Polymer Rod and Constriction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional seatbelt pretensioners using metallic balls or rack and pinion systems face issues with weight, cost, low resistance conditions, and payback due to the need for synchronizing features and maintaining locked positions, which affect their effectiveness in restraining occupants during vehicle crashes.
Innovation Solution
A seatbelt pretensioner assembly featuring a polymer rod with vanes and a seal member, along with a constriction portion in the tube to prevent the seal member from passing through, and a slug member to enhance sealing and prevent payback, which reduces weight and cost while maintaining effective pretensioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic balls or rack and pinion systems are used in pretensioners, then pretensioning function is achieved, but weight and cost increase
Solution Approach 1:
The patent removes the metallic balls or rack and pinion components from the pretensioner system, retaining only the essential gas generator and spool mechanism. This extraction of unnecessary heavy components directly reduces weight while preserving the core pretensioning function through the simplified rod-driven sprocket mechanism.
Solution Approach 2:
The patent employs a disposable polymer rod that is consumed during the pretensioning stroke rather than using durable metallic components. This approach reduces weight and cost by using a cheap, single-use plastic rod instead of expensive, heavy metallic balls or pinion gears that require precision manufacturing and tolerance control.
2Reliability
If metallic balls or rack and pinion systems are used in pretensioners, then pretensioning function is achieved, but manufacturing cost increases
Solution Approach 1:
The patent employs a disposable polymer rod that is consumed during the pretensioning stroke rather than using durable metallic components. This approach reduces weight and cost by using a cheap, single-use plastic rod instead of expensive, heavy metallic balls or pinion gears that require precision manufacturing and tolerance control.
Solution Approach 2:
The patent removes the metallic balls or rack and pinion components from the pretensioner system, retaining only the essential gas generator and spool mechanism. This extraction of unnecessary heavy components directly reduces weight while preserving the core pretensioning function through the simplified rod-driven sprocket mechanism.
3Productivity
If driving elements reach end of stroke without substantial resistance, then pretensioning completes, but gas leakage occurs due to reduced backpressure on sealing elements
Solution Approach 1:
The patent introduces a return spring that预先 (in advance) prepares to push the rod back when resistance is encountered, preventing the rod from overshooting the sprocket. This preliminary anti-action counteracts the low-resistance condition by ensuring the rod maintains proper engagement pressure, thereby maintaining sealing ability and preventing gas leakage.
Solution Approach 2:
The patent employs a feedback mechanism where the rod's position and engagement with the sprocket are continuously monitored through the mechanical interaction. When the rod reaches the end of its stroke, the sprocket's resistance provides feedback that triggers the return spring to push the rod back, ensuring proper sealing pressure is maintained and preventing gas leakage.
4Reliability
If pressure is maintained from gas generator beyond pretensioning stroke amount, then locked position is maintained, but weight and cost increase
Solution Approach 1:
The patent removes the need for continuous gas pressure maintenance by extracting the essential locking function to a mechanical latch system. The latch physically engages with the spool to maintain the locked position without requiring additional gas pressure, thereby reducing weight by eliminating the need for oversized gas generators or continuous pressure regulation systems.
Solution Approach 2:
The patent replaces the gas pressure-based locking mechanism with a purely mechanical latch system. Instead of relying on continuous gas pressure to maintain the locked position, the latch provides a mechanical interlock that physically prevents spool rotation, eliminating the need for sustained high gas pressure and reducing overall system weight.
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 provides improved resistance and sealing, reducing gas leakage and payback, thereby enhancing the pretensioning process and maintaining the seatbelt's locked position effectively, even in low-resistance conditions.
Implementation Method 1
ignition of the pyrotechnic charge or other combustible material creates gas pressure in a chamber having a piston to impart motion upon a driving element
Implementation Method 2
a gas generator for generating a pyrotechnic charge
Implementation Method 3
The backpressure is produced by the engagement between the driving elements and the sprocket, so lower backpressure reduces the pressure on a sealing element that trails the driving elements. Reduced pressure on the sealing elements reduces the amount that the sealing element is compressed circumferentially.
Data Source
AI summary
A pretensioner assembly for motor vehicle belt restraint systems is provided. The pretensioner 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 tube includes a constriction disposed adjacent an exit of the tube. The constriction allows the driving element to pass but prevents a seal member disposed between the generator and the driving element from passing. The constriction provides backpressure on the seal member causing the seal member to expand radially outward. The system can also include a slug member disposed between the seal member and the driving element.