Seatbelt Webbing Take-Up Spool With Low-Resistance Thrust Teeth
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Solution Overview
Problem
Existing webbing take-up devices face challenges in reducing resistance when engagement teeth of a rotating body interact with a moving member, which affects the efficiency of webbing take-up in seatbelt systems.
Innovation Solution
A webbing take-up device design featuring a rotating member with tapered thrust teeth and radial teeth, where the tapered portions of the thrust teeth are configured to decrease in dimension towards the radial outside, and the radial teeth are curved with a smaller radius than the moving member's outer peripheral profile, allowing for low resistance engagement and efficient rotation of the spool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If engagement teeth are made with uniform thickness, then manufacturing is simpler, but resistance increases when teeth engage with the moving member
Solution Approach 1:
The engagement teeth are designed with non-uniform thickness, where the thickness varies along the engagement direction. Specifically, the thickness is greater at the base section and gradually decreases toward the tip section. This local variation in geometry reduces resistance during engagement while maintaining manufacturing feasibility through standard machining processes.
Solution Approach 2:
The thickness parameter of the engagement teeth is changed along their length, transitioning from a uniform thickness design to a variable thickness design. The thickness dimension in the spool rotation circumferential direction is specifically reduced at the tip section compared to the base section, optimizing the engagement characteristics and reducing resistance.
2Strength
If engagement teeth have greater thickness, then structural strength is improved, but resistance when engaging the moving member increases
Solution Approach 1:
The engagement teeth exhibit local quality variations in thickness, with the base section having greater thickness for structural strength and the tip section having reduced thickness for lower engagement resistance. This localized differentiation allows the tooth to simultaneously achieve both strength and low resistance characteristics in different regions.
Solution Approach 2:
Rather than reducing the thickness of the entire tooth, only the tip portion is reduced in thickness while maintaining adequate thickness at the base section. This partial action approach preserves the necessary structural strength where needed while reducing resistance only in the engagement critical region.
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 significantly reduces resistance during engagement, enabling smoother and more efficient rotation of the spool, thereby enhancing the webbing take-up process and increasing the restraining force on occupants.
Implementation Method 1
the fluid supply unit provided at the axial direction base end side of the cylinder and configured to supply a fluid inside the cylinder in a vehicle emergency... When the pressure inside the cylinder rises as a result, the moving member provided inside the cylinder is moved toward the axial direction leading end side of the cylinder
Data Source
AI summary
A webbing take-up device including: a spool; a tube-shaped cylinder; a fluid supply unit; a rotating member including thrust teeth in a radial pattern about a rotation central axial line formed to faces that oppose one another in an axial direction, and including a tapered portion formed to a rotation outer peripheral side end portion of each of the thrust teeth and having a rotation axial direction dimension that decreases on progression toward a rotation radial direction outside, the spool being rotated in the take-up direction by the rotating member rotating toward one side; and a moving member that is moved toward the axial direction leading end side of the cylinder under pressure of the fluid to cause the rotating member to rotate toward the one side by being moved in an engaged state with the thrust teeth of the rotating member.