Webbing Take-up Device Cut-off Section Rotation Load
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Solution Overview
Problem
Webbing take-up devices face the challenge of preventing pull-out direction rotation force from being transmitted and output to the first rotation force transmission section via the second rotation force transmission section, especially when the rotation load exceeds a certain value.
Innovation Solution
The device incorporates a cut-off section that suppresses the transmission of rotation load by using a predetermined value calculated as the product of the gear ratio and maximum cogging torque, and a friction clutch that transmits rotation force using frictional force, ensuring that the rotation load is not transmitted to the first rotation force transmission mechanism when the pull-out direction rotation load is greater than this value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a friction clutch is provided in the reverse drive force transmission section to enable high-speed take-up rotation, then the spool can be rotated in the take-up direction at high speed, but pull-out direction rotation force may be transmitted and output to the forward drive force transmission section via the reverse drive force transmission section
Solution Approach 1:
A one-way clutch is introduced as an intermediary component in the reverse drive force transmission section. This one-way clutch allows rotation force transmission only in the take-up direction while blocking transmission in the pull-out direction, thereby preventing unwanted force transmission to the forward drive force transmission section while maintaining high-speed take-up rotation capability
Solution Approach 2:
The friction clutch in the reverse drive force transmission section is designed with dynamic engagement characteristics. It provides high friction force during take-up rotation to enable high-speed operation, while the one-way clutch dynamically blocks the transmission path during pull-out direction rotation, creating a dynamic transmission system that adapts to different rotation directions
2Power
If the friction clutch transmits rotation force in the second rotation force transmission mechanism, then the spool can rotate in the take-up direction, but rotation force from pull-out direction may be transmitted to the first rotation force transmission mechanism
Solution Approach 1:
The one-way clutch serves as a mediator between the friction clutch and the first rotation force transmission mechanism. It allows the friction clutch to transmit rotation force freely in the take-up direction while blocking any rotation force from the pull-out direction, preventing harmful force transmission to the forward drive force transmission section
Solution Approach 2:
The reverse drive force transmission section is segmented into two functional parts: the friction clutch for power transmission and the one-way clutch for directional control. This segmentation allows independent optimization of power transmission capability and harmful force blocking, with each component performing its specific function without interfering with the other
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 solution effectively suppresses the transmission of pull-out direction rotation force to the first rotation force transmission mechanism, preventing unwanted rotation and enhancing the stability of the webbing take-up process, even when the rotation load exceeds the predetermined value.
Implementation Method 1
the predetermined value of the rotation load is a product of a gear ratio of transmitting rotation force from the spool to the motor output shaft via the second rotation force transmission mechanism and a maximum value of a cogging torque of the motor
Implementation Method 2
the friction clutch transmits rotation force between the motor output shaft-side portion and the spool-side portion using frictional force arising between the spool-side portion and the motor output shaft-side portion of the friction clutch
Data Source
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AI summary
A webbing take-up device that includes: a cut-off section (60) that cuts off transmission of rotation load along a rotation force transmission route from a second rotation force transmission mechanism (58) to a spool via a first rotation force transmission mechanism (44) due to the rotation load in a pull-out direction becoming a predetermined value or greater; and a resistance section (40) that resists the rotation load during transmission of the rotation load, and that suppresses transmission of the rotation load along the rotation force transmission route in a case in which the rotation load is less than the predetermined value.