Capacitive Seatbelt Payout Sensor for Occupant Size Detection
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Solution Overview
Problem
Current occupant size identification methods for vehicle safety systems are cumbersome, requiring additional components that increase weight, cost, and package space, and are not efficiently integrated into seatbelt retractors.
Innovation Solution
A capacitive payout sensor system using a flexible parallel plate capacitor integrated within the seatbelt retractor, which measures seatbelt webbing length by changing capacitance values as the webbing is deployed, allowing for accurate occupant size determination and optimized safety measure deployment during crashes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional components are mounted outside the retractor for occupant size identification, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent combines the measurement function with the existing retractor by integrating a sensor that detects retractor spool rotation. This merges the measurement capability into the existing structure, eliminating the need for separate external measurement components while maintaining accurate seatbelt payout measurement for occupant size identification
Solution Approach 2:
The retractor spool serves multiple functions: it winds the seatbelt webbing and simultaneously acts as a measurement reference for detecting payout length. By making the spool multi-functional, the patent eliminates the need for dedicated external measurement devices, reducing component count while maintaining measurement capability
2Measurement precision
If additional measuring devices are added to the seatbelt system, then measurement accuracy is improved, but weight increases
Solution Approach 1:
The system uses the retractor spool's own rotation as the measurement reference, making the existing component serve the measurement function. This self-service approach eliminates the need for additional heavy external sensors and measurement devices, maintaining accurate payout measurement while minimizing weight increase
3Measurement precision
If external measurement components are mounted on the seatbelt system, then measurement capability is improved, but package space increases
Solution Approach 1:
The patent nests the measurement function within the existing retractor assembly by integrating a sensor that detects spool rotation internally. This nesting approach allows the measurement capability to be housed within the existing retractor volume, eliminating the need for additional external components and reducing the overall package space required
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
Enables precise determination of seatbelt webbing length based on occupant size, reducing the need for external components and improving the integration of safety systems within the vehicle, enhancing crash protection by deploying appropriate safety measures.
Implementation Method 1
A capacitive payout sensor system using a flexible parallel plate capacitor integrated within the seatbelt retractor, which measures seatbelt webbing length by changing capacitance values as the webbing is deployed
Data Source
AI summary
A seatbelt payout measuring device with a rewind spring having a first end connected to a center spool and a second end connected to a rewind spring housing. A dielectric material layered immediately adjacent to the rewind spring forming a first layer and an electrolytic coil with dielectric material layered on both sides forming a second layer, isolating the rewind spring from the electrolytic coil. A capacitive measuring device having a first lead connected to the first end of the rewind spring and a second lead connected to a first end of the electrolytic coil. The capacitive measuring device measuring capacitance with belt pullout.