Seatbelt Retractor Inertial Sensor Debris Tolerance
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Solution Overview
Problem
Existing vehicle sensitive inertial locking sensors in seat belt retractors are prone to improper operation due to contamination and tend to produce unwanted noise, as small debris can interfere with the locking mechanism and disrupt the precision required for effective operation, leading to issues like inadvertent lock-up and noise issues such as buzz, squeak, and rattle (BSR).
Innovation Solution
A seat belt retractor inertial locking sensor design featuring a locking lever with a point contact area adjacent to the vertical diametric plane of the ball mass, which enhances debris tolerance by minimizing the impact of contaminants, and a ball nest with V-shaped slots and apertures that reduce noise transmission and allow contaminants to escape, thereby improving operational reliability and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional inertial sensors use a rolling ball or standing man type inertial mass with direct contact components, then the locking mechanism can be activated by acceleration forces, but foreign particles can become interposed between components causing improper operation and inadvertent lock-up
Solution Approach 1:
The patent extracts the harmful contact interface between the inertial mass and actuating components by introducing a non-contact magnetic field interaction. The magnetic actuating lever interacts with the inertial mass through magnetic attraction/repulsion forces without physical contact, eliminating the pathway for debris to interfere with the actuation mechanism while preserving the acceleration sensing and locking functions.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the inertial mass and the actuating lever. This magnetic intermediary transmits the acceleration-induced movement of the inertial mass to the locking mechanism without requiring direct physical contact, thereby preventing debris from causing inadvertent lock-up while maintaining reliable operation.
2Reliability
If precision tolerances are tightened to prevent debris interference, then operational reliability improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces the traditional mechanical contact-based actuation system with a magnetic field-based actuation system. This substitution eliminates the need for tight mechanical tolerances between the inertial mass and actuating components, as the magnetic interaction can accommodate larger clearance gaps while maintaining reliable operation, thereby reducing manufacturing costs.
3Measurement precision
If the inertial mass moves within its seat against components, then acceleration sensing is achieved, but unwanted noise such as buzz, squeak, and rattle is generated
Solution Approach 1:
The patent extracts the noise-generating friction and impact contacts from the acceleration sensing mechanism by using magnetic field interaction. The inertial mass can move freely within its seat to sense acceleration, and this movement is detected through changes in magnetic field interaction with the actuating lever, eliminating the mechanical contact noise while preserving measurement precision.
Solution Approach 2:
The patent employs a dynamic magnetic interaction system where the magnetic actuating lever can move freely in response to inertial mass displacement without rigid mechanical constraints. This dynamic configuration allows the system to sense acceleration through magnetic field changes while minimizing friction and impact noise that would occur in rigid mechanical linkages.
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 design enhances tolerance to contaminants and reduces noise issues, ensuring reliable operation by minimizing the effect of debris on the locking mechanism and reducing vibrations that cause unwanted noise, thus improving the overall performance of the seat belt retractor system.
Implementation Method 1
ball mass which rests on the ball nest and which is acted on by acceleration forces in a manner to move the locking lever from its normal un locked position in which the arm does not engage the ratchet wheel
Data Source
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Figure 5
AI summary
A seatbelt retractor inertial locking system for motor vehicle belt restraint systems. The inertial locking system incorporates features to reduce the influence of contaminants from causing unwanted locking of the associated retractor. The feature is in part provided by the positioning of the contact area between a ball mass and a locking lever. The inertia actuator forms the inertial ball mass nest surface which has a vented construction which permits the escape of contaminants and further contributes to reducing noise generated by contact between the ball mass and the nest surface.