Fixture for Webbing Take-Up Device Cylinder Attachment
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Solution Overview
Problem
Existing webbing take-up devices face challenges in accurately attaching cylindrical members, such as pretensioner cylinders, to the frame due to dimensional errors and deformation during press-molding of pipe-shaped members, leading to inconsistent contact and improper attachment.
Innovation Solution
A fixture with a fixing portion and a contact portion is designed to securely attach cylindrical members to the frame, utilizing point- or line-contact mechanisms to ensure precise positioning and retention, even with dimensional errors, by integrating with the frame's structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pipe-shaped member is press-molded into a cylinder to reduce cost, then manufacturing cost is reduced, but dimensional accuracy and shape precision deteriorate due to deformation and molding errors
Solution Approach 1:
The invention changes the attachment mechanism from direct rigid attachment to elastic deformation-based attachment. The fixture body is designed to elastically deform during assembly, allowing the contact portion to adapt to dimensional variations in the cylinder while maintaining secure attachment. This parameter change in the attachment mechanism resolves the contradiction by making the system tolerant of manufacturing precision variations.
Solution Approach 2:
The fixture is segmented into distinct functional portions: a fixing portion for attachment to the frame and a contact portion for interacting with the cylinder. This segmentation allows each portion to be optimized independently - the fixing portion provides stable mounting while the contact portion accommodates dimensional variations through elastic deformation, thereby resolving the contradiction between ease of manufacture and manufacturing precision.
2Ease of operation
If the fixture uses a concave curved surface to contact the cylinder, then ease of assembly is improved, but attachment reliability deteriorates due to inconsistent contact caused by dimensional errors
Solution Approach 1:
The fixture body is designed to elastically deform during assembly, transitioning from a rigid structure to a dynamic, adaptive structure. This elastic deformation allows the contact portion to automatically adjust to dimensional variations in the cylinder, ensuring consistent point or line contact regardless of manufacturing tolerances. The dynamic behavior resolves the contradiction by maintaining attachment reliability while preserving ease of assembly.
Solution Approach 2:
The invention changes the mechanical state of the fixture from rigid to elastically deformable during assembly. This parameter change in stiffness allows the fixture to accommodate dimensional errors in the cylinder while maintaining reliable attachment. The elastic deformation capability enables the fixture to adapt its contact characteristics dynamically, resolving the contradiction between ease of assembly and attachment reliability.
Data Source
AI summary
A fixture is disclosed which can reliably attach an attachment member, such as a cylinder, to an attachment site, such as a frame. The fixture includes a fixing portion, which faces the attachment site at the side of the attachment site and is fixed to the attachment site, and a contact portion, which is disposed at the side opposite from the attachment site, with the attachment member therebetween. The contact portion is integrally coupled to the fixing portion, point-contacts or line-contacts the attachment member, and is configured to push the attachment member to the attachment site in a state where the fixing portion is fixed to the attachment site. A webbing take-up device including this fixture is also disclosed.