Webbing Take-up Device Motor Fixation with Tightening Margin
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Solution Overview
Problem
Webbing take-up devices that rotate a spool using motor drive force often suffer from operation noise due to variations in the separation between the rotation shafts of the motor and the gears, leading to unstable meshing and increased noise during spool rotation.
Innovation Solution
A webbing take-up device configuration that includes a spool, a motor with a rotation shaft and engaging portion, a first gear fixed to the rotation shaft, a second gear that meshes with the first gear, and a housing with a second gear support portion, where the motor is fixed to the housing with a tightening margin between the engaging and engaged portions, reducing variation in shaft separation and stabilizing gear meshing to minimize operation noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the motor is fixed rigidly to the housing without tightening margin, then the structural stability is improved, but the gear meshing stability deteriorates due to shaft separation variation
Solution Approach 1:
The patent changes the fixation parameter by introducing a tightening margin between the motor's engaging portion and the housing's engaged portion. This margin allows controlled movement of the motor shaft, compensating for manufacturing tolerances and preventing excessive separation variation that would cause gear meshing instability and noise.
Solution Approach 2:
The patent introduces dynamic flexibility into the motor fixation system. Instead of rigid fixation, the tightening margin enables the motor to adjust its position dynamically, maintaining optimal gear meshing conditions while allowing for thermal expansion and manufacturing variations.
2Reliability
If the tightening margin between engaging portion and engaged portion is increased, then the gear meshing stability is improved, but the structural rigidity deteriorates
Solution Approach 1:
The patent optimizes the tightening margin parameter to achieve a balance between gear meshing stability and structural rigidity. The margin is sized to accommodate shaft separation variation without being so large as to compromise the overall structural integrity and motor fixation stability.
3Ease of manufacture
If rigid fixation of motor to housing is used, then the ease of manufacture is improved, but the operation noise increases due to unstable gear meshing
Solution Approach 1:
The patent modifies the fixation parameter by incorporating a tightening margin, which maintains manufacturing simplicity while significantly reducing operation noise. The margin compensates for manufacturing tolerances in gear and shaft dimensions, ensuring stable meshing without requiring complex assembly procedures.
Data Source
AI summary
A webbing take-up device includes a spool on which a webbing worn by an occupant is taken up, and a motor that includes a rotation shaft and a first boss portion disposed coaxially with the rotation shaft. The webbing take-up device further includes an A-gear that is fixed to the rotation shaft, and a B-gear that meshes together with the A-gear and that is rotated by the A-gear being rotated such that the spool is rotated. The webbing take-up device further includes a gear housing that includes a B-gear support portion on which the B-gear is supported, and an engaged hole engaged by the first boss portion so as to have tightening margin therebetween, and to which the motor is fixed in a state in which the first boss portion has engaged with the engaged hole.