Webbing Winding Device Piston Engagement Mechanism
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Solution Overview
Problem
In webbing winding devices, the load value of the force limiter load can change unexpectedly due to piston movement reversal, leading to unintended re-meshing between the claw and torque tube, which alters the load value from low to high, compromising safety and functionality.
Innovation Solution
A webbing winding device design that includes a pawl capable of changing the force limiter load value, a piston with an engagement portion that prevents return to the standby position, and a stopper to restrict movement, ensuring the pawl remains in the release position and maintaining the desired load value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the piston is allowed to move freely between standby position and maximum movement position, then the device can operate with simple structure, but the piston may return to standby position due to reaction force, causing unintended re-meshing and load value changes
Solution Approach 1:
The engagement portion (hook portion) is designed to engage with the engaged portion before the piston can return to the standby position due to reaction force. This preliminary engagement prevents the harmful reverse movement before it can occur, maintaining the pawl in the release position and preventing unintended re-meshing between the claw and torque tube.
Solution Approach 2:
The engagement portion acts as an intermediary mechanism between the piston and the engagement surface. The hook portion engages with the engaged portion to mediate the piston's movement, allowing forward movement while preventing backward movement, thus controlling the piston position without requiring complex locking mechanisms.
2Reliability
If the piston is constrained to prevent return movement, then the load value stability is improved, but the device structure becomes more complex
Solution Approach 1:
The piston structure is segmented into functional portions: the arm portion that moves linearly, the engagement portion (hook portion) that provides one-way constraint, and the connection to the pawl. This segmentation allows each portion to perform its specific function independently, achieving reliable load value stability through the engagement portion while keeping the overall structure relatively simple.
Solution Approach 2:
Instead of using a complex locking mechanism to prevent piston return, the design uses a simple hook-shaped engagement portion that naturally engages with the engaged portion. The geometry of the hook and engagement surface inherently prevents reverse movement without requiring additional locking components, thus achieving constraint with minimal added 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
Prevents unintended changes in the force limiter load value by preventing piston return to the standby position, maintaining the desired load value and ensuring consistent operation during vehicle deceleration and rapid rotation.
Implementation Method 1
an engagement portion which includes an arm portion provided in the piston so as to be elastically deformable and a hook portion provided protruding from the arm portion toward a side of the engaged portion, the engagement portion permitting movement of the piston toward the one side in the movement direction by the hook portion sliding on the engaged portion so that the arm portion is elastically deformed, and the engagement portion restricting movement of the piston toward the other side in the movement direction by the hook portion engaging with the engaged portion
Data Source
AI summary
In a webbing winding device, even when a piston moves toward the other side in a movement direction due to a reaction when the piston moves to a maximum movement position, an engagement surface of a hook portion comes into contact with a subject engagement surface of a subject engagement portion, so that the movement of the piston toward the other side in the movement direction is restricted. Accordingly, the piston is prevented from returning to a standby position, and a pawl is prevented from returning to a lock position. For this reason, a state where a rotation of a locking ring in the pull-out direction is maintained. Accordingly, after the piston moves from the standby position to the maximum movement position, the piston is prevented from returning to the standby position, and the force limiter load is prevented from being changed.