Webbing Take-Up Device Rotor Teeth
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Solution Overview
Problem
Existing webbing take-up devices experience high resistance when the moving member engages with the rotor's engaging teeth, which hampers efficient kinetic energy transmission and webbing take-up during emergency vehicle situations.
Innovation Solution
The design incorporates a rotor with engaging teeth that have a smaller thickness dimension on one side of the base portion, a reduced inclination angle on the pull-out side, and surfaces extending parallel to the rotation axis, reducing the volume and friction when the moving member engages, thereby minimizing resistance and enhancing kinetic energy transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the moving member engages with the engaging teeth of the rotor to transmit kinetic energy, then the webbing take-up function is achieved, but resistance increases reducing transmission efficiency
Solution Approach 1:
The engaging tooth is designed with non-uniform thickness along its height, creating different local properties: the upper portion has smaller thickness to reduce resistance during engagement, while the lower portion has larger thickness to maintain structural strength and proper kinetic energy transmission. This local quality variation resolves the contradiction between reducing engagement resistance and maintaining transmission efficiency.
Solution Approach 2:
The engaging tooth exhibits asymmetric geometry with respect to its thickness distribution. The thickness dimension varies along the height of the tooth, being smaller at the upper engagement surface and larger at the base. This asymmetric design optimizes the engagement process by reducing contact resistance while preserving the structural integrity needed for effective energy transmission.
2Ease of operation
If the thickness dimension of the engaging tooth is reduced to minimize resistance, then engagement smoothness improves, but the structural strength of the rotor may be compromised
Solution Approach 1:
The engaging tooth is designed with non-uniform thickness along its height, creating different local properties: the upper portion has smaller thickness to reduce resistance during engagement, while the lower portion has larger thickness to maintain structural strength and proper kinetic energy transmission. This local quality variation resolves the contradiction between reducing engagement resistance and maintaining transmission efficiency.
Solution Approach 2:
Instead of uniformly reducing the tooth thickness in one dimension, the design varies the thickness along the height dimension of the tooth. This dimensional variation allows the upper engagement surface to have minimal thickness for smooth operation, while the lower portion maintains sufficient thickness for structural strength, effectively resolving the contradiction through multi-dimensional design optimization.
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
This configuration reduces resistance and improves the efficiency of kinetic energy transmission, allowing for smoother webbing take-up and potentially smaller device sizes with reduced operational costs.
Implementation Method 1
activation of a gas generator
Implementation Method 2
transmitting kinetic energy of the moving member that is moved by activation of the gas generator to the spool efficiently
Data Source
AI summary
A webbing take-up device is provided with (i) a spool and (ii) a rotor rotatable integrally with the spool having a base portion and radially-extending engaging teeth. A webbing to be applied to a vehicle occupant is wound around the spool. Each engaging tooth protrudes from the base portion in a rotation axis direction of the spool, and is tapered along the rotation axis direction such that a thickness dimension in a rotation circumference direction of the spool of a portion of the engaging tooth at the opposite side thereof from the base portion becomes smaller toward the base portion side thereof. The axially-tapered shape of the engaging teeth reduces stresses and improves transmission efficiency between the rotor teeth and the teeth of a moving member engaged thereto.