Vehicular seat back frame structure
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Solution Overview
Problem
The existing vehicular seatback frame structures with closed cross-sectional structures are over-engineered, leading to increased weight and potential separation issues at bonded sections due to adhesive agent limitations, and pose challenges in productivity and material cost due to complex shapes and large adhesive coating areas.
Innovation Solution
A vehicular seatback frame structure featuring two resin side frames with an upper cross member formed by a first member with a downward opening part and a second member with an upward opening part, positioned to create a closed cross-sectional structure, where the joining parts are strategically located to reduce stress concentration and adhesive usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a closed cross-sectional structure is formed by bonding two members with adhesive agent, then the rigidity and strength of the seatback frame are improved, but the bonding section may separate under collision loads due to adhesive strength limitations
Solution Approach 1:
The first member and second member are integrally formed as a single piece, eliminating the adhesive bonding interface between them. This merging of components removes the weak bonding section that could separate under load, while the integral construction maintains the closed cross-sectional structure for required rigidity and strength.
Solution Approach 2:
The upper cross member is divided into two functional parts (first member and second member) that are positioned to form a closed cross-sectional structure, but manufactured as one integral component. This segmentation allows optimization of each part's geometry while avoiding the bonding reliability issue through integral construction.
2Strength
If all seatback frame components are formed with closed cross-sectional structure, then the rigidity is improved, but the weight increases due to overspecification
Solution Approach 1:
The closed cross-sectional structure is applied locally only to the upper cross member where high rigidity is required for collision resistance, while other seatback frame components can use lighter open cross-sectional structures. This localized application of the closed structure avoids unnecessary weight increase in areas where high rigidity is not critical.
3Adaptability or versatility
If the headrest supporting section is formed in a complicated shape, then the functional requirements are met, but the degree of difficulty in forming increases and productivity decreases
Solution Approach 1:
The complex headrest supporting section geometry is built-in during the integral molding process of the first and second members, rather than requiring subsequent complex assembly or joining operations. This preliminary formation of the complicated shape in a single manufacturing step maintains productivity while achieving the required headrest support functionality.
4Strength
If outer frame member and inner frame member are bonded by adhesive agent, then the closed cross-sectional structure is formed, but the coated area and coating amount of adhesive agent increase, deteriorating workability and increasing material cost
Solution Approach 1:
The outer frame member and inner frame member are merged into a single integral component (first member and second member), eliminating the need for adhesive bonding between them. This removes the workability issues associated with large-area adhesive coating while maintaining the structural integrity of the closed cross-sectional configuration through integral construction.
Data Source
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AI summary
Separation of a joining in a joining part of a closed cross-sectional structure of an upper cross member is suppressed and the rigidity of the upper cross member is ensured. A vehicular seatback frame structure is provided with resin side frames (21, 22), and an upper cross member (30) bridged over between upper parts of the side frames (21, 22). The upper cross member (30) includes a first member (31), and a second member (32) disposed under the first member (31). An opening part is provided in a lower part of the first member (31), the first member (31) has a traverse cross-sectional shape opening to the downward side, an opening part is provided in an upper part of the second member (32), and the second member (32) has a traverse cross-sectional shape opening to the upward side. The opening part of the first member (31) and the opening part of the second member (32) are bonded in a state of facing each other to form a closed cross-sectional structure.