Seat Belt Retractor Inertial Sensor Vibration and Contamination Protection
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Solution Overview
Problem
Seat belt retractors fail to operate effectively in severe environments like mud and snow due to premature lock-up caused by vehicle bouncing and contamination, which leads to improper functioning.
Innovation Solution
A sealed chamber with an inertial sensor and a magnetic system that prevents excessive movement of the sensor mass, combined with a seal and cover design to prevent contaminants from entering, ensuring the retractor operates correctly in harsh conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inertial sensor is exposed to the external environment, then the retractor can detect vehicle deceleration, but the sensor becomes susceptible to contamination and excessive movement causing premature lock-up
Solution Approach 1:
The patent divides the retractor into separate functional chambers: a sealed sensor chamber containing the inertial sensor isolated from contaminants, and an external environment exposed to mud and snow. The seal between the cover and frame creates distinct environmental zones, protecting the sensor while maintaining deceleration detection capability.
Solution Approach 2:
The magnetic force field acts as an intermediary between the magnet and the movable mass, transmitting the restraining force without physical contact. This contactless magnetic coupling allows the mass to respond to deceleration while being restrained by the magnet, preventing excessive movement that would cause premature lock-up.
2Measurement precision
If the movable mass is freely movable in the inertial sensor, then the sensor can accurately detect deceleration, but the mass moves excessively during vehicle bouncing causing premature lock-up
Solution Approach 1:
The patent replaces a purely mechanical restraint system with a magnetic field-based restraint system. The magnet generates a magnetic force that acts on the movable mass, providing a contactless restraining force that limits the mass's movement during vehicle bouncing while still allowing accurate deceleration detection.
3Reliability
If the seal prevents contaminants from entering the sensor chamber, then the sensor is protected, but the seal adds complexity to the retractor assembly
Solution Approach 1:
The patent combines the seal function with the cover structure. The seal is integrated between the cover and the frame, merging the protective sealing function with the existing cover assembly rather than adding a separate, complex sealing system. This integration protects the sensor while minimizing additional complexity.
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 effectively prevents premature lock-up and contamination, ensuring the seat belt retractor functions reliably on rough, muddy, and snow-laden roads and trails by stabilizing the inertial sensor and sealing out contaminants.
Implementation Method 1
a magnet 36 spaced from the mass 34 to create a magnetic force upon the mass 34 preventing the magnet from moving excessively if the retractor is subject to predetermined levels of vibration
Data Source
AI summary
A seat belt retractor (10) having a frame with sides (14, 16) and a cover associated with at least one side, an inertial sensor (30) positioned between the at least one side of the frame and the cover, a seal located between the cover and the frame side to prevent contaminants from entering a space about the inertial sensor, the inertia sensor including a movable mass (34) and a magnet (36) spaced from the mass (34) to create a magnetic force upon the mass (34) preventing the magnet from moving excessively if the retractor is subject to predetermined levels of vibration.