Webbing Take-Up Device Spring Durability
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Solution Overview
Problem
The durability of friction springs in webbing take-up devices is compromised due to repeated deformations, leading to reduced performance and reliability in vehicle seatbelt systems.
Innovation Solution
A webbing take-up device design featuring a spool, rotating bodies, a spring with a coil portion, and a lever that enlarges the spring's diameter to transmit rotation, with catch portions to manage stress and alleviate bending stress, enhancing the spring's durability through strategic engagement and movement of spring ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a friction spring is used to transmit rotation in the webbing take-up device, then the rotation transmission function is achieved, but the durability of the spring deteriorates due to repeated deformations
Solution Approach 1:
The patent changes the structural parameters of the spring by providing terminal ends that can abut against catch portions or move while remaining caught. This parameter change allows the spring to distribute stress differently during deformation, preventing concentration at single points and thereby improving durability under repeated deformations
Solution Approach 2:
The spring is segmented into distinct functional portions: a coil portion for elastic deformation and terminal ends for stress management. The terminal ends are further divided into first and second terminal ends with different engagement modes (abutting vs. moving caught), creating segmentation that distributes mechanical stress across multiple locations and reduces wear on any single point
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 increases the durability of the spring by dispersing stress and alleviating bending stress, allowing for improved performance and reliability in repeated deformations, while also preventing excessive force application on components.
Implementation Method 1
a spring that is provided between the first rotating body and the second rotating body, and that includes a coil portion wound into a ring shape along an outer circumferential portion of the first rotating body... enlarges a diameter of the coil portion by moving the end portion at the another side of the spring toward one side in the circumferential direction
Implementation Method 2
in a case in which the lever is rotated toward the one side in the circumferential direction of the first rotating body, at least one of a terminal end of the end portion at the one side of the spring or a terminal end of the end portion at the another side of the spring abuts either the first spring catch portion or the second spring catch portion
Data Source
AI summary
A webbing take-up device includes a second clutch that transmits rotation of a motor to a spool. The second clutch includes a base including a first spring catch portion, a clutch gear, a clutch spring including a coil portion, having an end portion at one side caught to the first spring catch portion, and a lever that includes a second spring catch portion catching an end portion at another side of the clutch spring, and that enlarges diameter of the coil portion to abut the clutch gear by moving the end portion at the another side of the clutch spring toward one side in the circumferential direction of the base. A terminal end of the end portion at the one side of the clutch spring abuts the first spring catch portion when the lever is rotated toward the one side in the circumferential direction of the base.