Webbing Retractor Force Limiter Switching Mechanism
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Solution Overview
Problem
Existing webbing retractors fail to effectively set a high limit load for a force limiter mechanism at an early stage, particularly for vehicle occupants with larger physiques, leading to inadequate restraint during emergencies.
Innovation Solution
A webbing retractor design incorporating a take-up shaft, pretensioner mechanism, and force limiter mechanism with switching components that allow the limit load to be switched from a low to a high load, enabled by a pretensioner mechanism operation, ensuring early high load application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the limit load is set to low level from the beginning, then the device complexity is reduced, but the restraint force is insufficient for occupants with large physique at early stage
Solution Approach 1:
The patent applies preliminary action by pre-configuring the force limiter mechanism with multiple limit load levels (low and high) and using a switching device that can transition between these levels. The switching device is designed in advance to respond to pretensioner operation, enabling the system to automatically select the appropriate limit load level based on the emergency situation and occupant characteristics without requiring complex real-time adjustments.
2Force
If the limit load is switched to high level after pretensioner operation, then the restraint force is improved for large physique occupants, but the response time is delayed
Solution Approach 1:
The patent implements feedback by using the pretensioner mechanism's operation as a trigger signal for the switching device. When the pretensioner operates during an emergency, it generates a mechanical or positional change that is detected by the switching device, which then automatically switches the limit load from low to high level. This feedback loop ensures that the high limit load is applied at the appropriate moment (during emergency) without requiring separate sensors or complex control systems, thereby minimizing response time while maintaining safety.
3Adaptability or versatility
If a switching device is added to change limit load levels, then the adaptability to different occupant physiques is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the force limiter mechanism to serve multiple functions: it can operate at both low and high limit load levels using the same basic mechanical structure. The switching device integrates with the existing pretensioner mechanism, allowing the system to adapt to different occupant physiques (from small to large) without requiring entirely separate mechanisms for each load level. This multi-functionality reduces the need for duplicate components and simplifies the overall system architecture.
Data Source
AI summary
In a webbing retractor, due to operation of a pretensioner mechanism, a stopper wire is moved, and second lock pawls of a second lock base mesh-together with an inner ratchet of a lock ring. In this way, a limit load by a torsion shaft can be switched to a high load. Therefore, immediately after operation of the pretensioner mechanism, the limit load by the torsion shaft can be made to be to the high load, and the limit load can be made to be the high load at an early stage.