Seatback Back Frame Stress Distribution via Extending Portion
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Solution Overview
Problem
The existing back side frames in seatbacks are prone to cracking due to rotational moments, which can be mitigated by increasing thickness, but this leads to higher production costs and mass.
Innovation Solution
Incorporating an extending portion from the stopper that is fixed to the back side frame, allowing the moment to be dispersed and reducing maximum stress, thereby preventing cracks without increasing production cost or mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the back side frame member is increased to prevent cracks, then the strength and reliability are improved, but the production cost and mass increase
Solution Approach 1:
The patent extends the stopper in the longitudinal direction to create an extending portion that distributes stress along the length of the component rather than concentrating it at a single point. This dimensional extension allows the same material thickness to withstand higher loads by spreading the moment across a longer structure, thereby preventing cracks without increasing mass.
2Strength
If the thickness of the back side frame member is increased to prevent cracks, then the strength is improved, but the production cost increases
Solution Approach 1:
By extending the stopper longitudinally, the patent creates a stress-distributing structure that achieves higher moment resistance without requiring thicker material. This dimensional approach maintains manufacturing simplicity and material cost efficiency while achieving the required strength through geometric optimization rather than material quantity increase.
3Duration of action of stationary object
If the stopper is made thicker to resist repeated moments, then the durability is improved, but the mass and production cost increase
Solution Approach 1:
The longitudinal extension of the stopper creates a distributed stress path that reduces peak stresses during repeated loading cycles. This extends the service life of the back side frame by preventing fatigue crack initiation and propagation, while maintaining the original material thickness and mass, thereby improving durability without the penalty of increased weight.
Data Source
AI summary
A back frame, which forms a framework of a seatback, includes a back side frame, a stopper, and an extending portion. The back side frame is rotatable with respect to a cushion frame in seat front-rear directions. The stopper is fixed to the back side frame and includes a contact portion. When the contact portion contacts a contact target portion that is immobile with respect to the cushion frame, the stopper restricts rotation of the back side frame. The extending portion extends from the stopper in the seat front-rear directions. The extending portion is fixed to the back side frame in at least a part of the extending portion.