Vehicle Seat Belt Force Limiter Activation Detection
Solution Overview
Problem
Conventional vehicle seat belt systems without a pretensioner face challenges in detecting the activation of a force limiter, which can lead to unsafe use of the webbing after the force limiter has been activated, as existing methods rely on the pretensioner's initiator for detection.
Innovation Solution
A vehicle seat belt system that includes a buckle with a force limiter and a warning section, which utilizes the movement of the buckle to notify the occupant of the force limiter's activation, either through electrical detection or visual indicators, ensuring the webbing is not reused after activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a force limiter is provided on the buckle side without a pretensioner, then the tensile load on the webbing is reduced upon activation, but the ability to detect the activation of the force limiter is lost
Solution Approach 1:
An electrical circuit is introduced as an intermediary detection mechanism. The circuit includes a movement detection switch that is normally closed when the buckle is in its initial position. When the force limiter activates and the buckle moves, the switch opens, changing the electrical circuit state from closed to open. This electrical intermediary allows detection of the mechanical movement without requiring a pretensioner.
Solution Approach 2:
The mechanical detection method (relying on pretensioner initiator disconnection) is replaced with an electrical detection system. The movement detection switch converts the mechanical displacement of the buckle into an electrical signal change, allowing the control unit to detect force limiter activation through electrical means rather than mechanical means.
2Force
If the buckle moves to reduce tensile load upon pretensioner activation, then the force limiter performs its shock absorption function, but the webbing cannot be safely reused afterward
Solution Approach 1:
The system implements feedback by continuously monitoring the electrical circuit state through the movement detection switch. When the force limiter activates and causes buckle movement, the switch opens and sends a signal to the control unit. The control unit then provides feedback to the occupant through a warning device (such as a warning light), clearly indicating that the force limiter has activated and the webbing should not be reused, ensuring safety through informative feedback.
3Difficulty of detecting and measuring
If conventional detection methods are used relying on pretensioner initiator disconnection, then activation can be detected electrically, but this method is not applicable when no pretensioner is present
Solution Approach 1:
The movement detection switch serves multiple functions: it detects buckle movement caused by force limiter activation, it provides a closed circuit signal during normal operation, and it opens the circuit when movement occurs. This universal detection mechanism works regardless of whether a pretensioner is present, making the system adaptable to both pretensioner-equipped and pretensioner-less seat belt configurations.
Data Source
AI summary
There is provided a vehicle seat belt system including: webbing that has one end anchored to one seat width direction side surface of a vehicle seat or to a vehicle body, and that restrains an occupant seated in the vehicle seat; a retractor to which another end of the webbing is engaged and that is configured to take up the webbing, the retractor being provided with a pretensioner which, when activated, pulls in the webbing; a buckle, with which a tongue plate attached to the webbing can be engaged; a force limiter that allows the buckle to move to thereby reduce a tensile load acting on the webbing due to activation of the pretensioner; and a warning section that is configured to utilize movement of the buckle resulting from the force limiter to notify the occupant of an abnormality that the force limiter has been activated.