Webbing Take-up Device Compact Gear Arrangement
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Solution Overview
Problem
Existing webbing take-up devices face challenges in reducing size for vehicle installation while maintaining effective webbing take-up and noise reduction.
Innovation Solution
A webbing take-up device design featuring a spool, motor, and multiple rotating bodies with specific gear configurations that transmit rotation force efficiently, reducing the axial center distance and allowing for a compact design, and controlling the reduction ratio to minimize clutch weight centrifugal force and motor speed, thereby reducing noise and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the axial center distance between rotating bodies is reduced to achieve compact size, then the device size is reduced, but the rotation force transmission efficiency may deteriorate
Solution Approach 1:
The patent applies nesting by arranging multiple rotating bodies (first through fifth rotating bodies) in a compact configuration where their axial centers are positioned between the axial centers of the third and fifth rotating bodies. This nested arrangement allows efficient rotation force transmission while maintaining a compact overall device size, as each rotating body is strategically positioned within the limited space defined by the third and fifth rotating bodies' axial centers.
Solution Approach 2:
The patent utilizes dimensional optimization by carefully controlling the spatial arrangement of rotating bodies along the axial direction. By positioning the axial centers of the first, second, fourth, and input portion rotating bodies between the axial centers of the third and fifth rotating bodies, the design optimizes the axial dimension to achieve compact size while maintaining effective rotation force transmission through proper gearing relationships.
2Object-generated harmful factors
If the reduction ratio from the first rotating body to the input portion is increased to reduce motor speed and noise, then the operation noise is reduced, but the revolution speed of the clutch weight increases causing increased centrifugal force
Solution Approach 1:
The patent applies parameter changes by optimizing the reduction ratio relationship between different gear stages. Specifically, it sets the reduction ratio from the first rotating body to the input portion at no more than twice the reduction ratio from the output portion to the fifth rotating body. This parameter optimization balances motor speed reduction (for noise reduction) with clutch weight speed control (to limit centrifugal force), achieving a compromise that satisfies both requirements.
3Productivity
If the mass of the clutch weight is increased to improve take-up performance, then the take-up performance is improved, but the device size and noise increase
Solution Approach 1:
The patent optimizes the clutch weight mass parameter by controlling the reduction ratio relationship. By limiting the reduction ratio from the first rotating body to the input portion to no more than twice the reduction ratio from the output portion to the fifth rotating body, the design ensures that the clutch weight does not need to be excessively large to achieve effective take-up performance. This parameter optimization allows adequate take-up performance while maintaining compact device size and acceptable noise levels.
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 achieves a compact size for the webbing take-up device, suppresses operation noise, and allows for safe and efficient webbing take-up and release, enhancing the device's usability and performance.
Implementation Method 1
a clutch weight that is moved toward an outer side in a radial direction of rotation by being rotated together with the input portion
Data Source
AI summary
A webbing take-up device includes a spool, a motor that includes a rotation shaft, and an A-gear, a B-gear, a holder gear, an input gear, a clutch gear, an idle gear, and a spool gear that transmit rotation of the rotation shaft to the spool. The webbing take-up device further includes clutch weights that are moved toward a rotation-radial direction outside by being rotated together with the input gear such that rotation force of the input gear is transmitted to the clutch gear. Moreover, axial centers of rotations of the A-gear, the B-gear, the input gear and the clutch gear, and the idle gear are disposed between an axial center of rotation of the holder gear and an axial center of rotation of the spool gear.