Webbing Take-Up Device Restriction Mechanism
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Solution Overview
Problem
Existing webbing take-up devices face challenges in preventing the moving member from moving towards the axial direction base end side due to spool rotation in the pull-out direction, which can lead to unintended movement and reduced effectiveness in vehicle emergencies.
Innovation Solution
A webbing take-up device incorporating a spool, rotating member, and restriction portion, where the moving member is guided and deformed to engage with the rotating member, and a tube-shaped member under fluid pressure, with a restriction portion positioned to prevent movement towards the axial direction base end side, effectively restricting the rotating member and spool from rotating in the pull-out direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the moving member is allowed to move freely in the axial direction, then the device complexity is reduced, but the reliability deteriorates due to unintended movement towards the axial direction base end side
Solution Approach 1:
The restriction portion acts as an intermediary element between the moving member and the tube-shaped member. It engages with the deformed portion of the moving member to prevent unintended axial movement towards the base end side, while allowing controlled movement towards the leading end side for normal operation. This intermediary structure resolves the contradiction by providing selective constraint without requiring complete immobilization mechanisms.
2Reliability
If the restriction portion is positioned to effectively prevent movement, then the reliability is improved, but the device complexity increases due to additional positioning requirements
Solution Approach 1:
The restriction portion is pre-positioned within the tube-shaped member at a location that corresponds to the maximum engagement range position of the rotating member. This preliminary positioning ensures that when the moving member deforms and attempts to move towards the base end side, it automatically engages with the restriction portion without requiring additional sensors or active control systems. The positioning is built into the structure during assembly.
Solution Approach 2:
The moving member's own deformation characteristic is utilized to engage with the restriction portion. When the moving member is pressed by the engagement portion and attempts to return towards the base end side, its deformation causes it to naturally contact the restriction portion, which then prevents further unwanted movement. The system uses the moving member's inherent mechanical properties rather than requiring external control mechanisms.
3Reliability
If the moving member is constrained to prevent pull-out direction rotation, then the reliability is improved, but the ease of operation worsens due to restricted movement freedom
Solution Approach 1:
The restriction portion provides dynamic constraint rather than static immobilization. It allows the moving member to move freely towards the leading end side for normal take-up operation, while dynamically engaging to prevent movement towards the base end side when deformation occurs. This dynamic behavior maintains ease of operation for intended functions while providing reliability for preventing unintended movements.
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 restricts the moving member's movement towards the axial direction base end side, preventing spool rotation in the pull-out direction, thereby enhancing the device's ability to maintain webbing tension and effectively restrain occupants during vehicle emergencies.
Implementation Method 1
Under pressure of a fluid supplied to another end side of the moving member, the moving member is moved toward the axial direction leading end side
Data Source
AI summary
In a webbing take-up device, when a rotating member is rotated in a take-up direction in a state in which first engagement teeth and second engagement teeth of a rotating member are digging or biting into a moving member, the moving member is pressed by the first engagement teeth and the second engagement teeth of the rotating member. The moving member thus expands into a first deformation-permitting portion and a second deformation-permitting portion in a cover plate, and expanded portions of the moving member oppose a first restriction portion configured by an axial center direction leading end face of a cylinder, and a second restriction portion of the cover plate.