Vehicle Roof Side Rail Variable Cross-Section Collision Load Management
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Solution Overview
Problem
The existing vehicle structure body design, where roof side rails are joined to center pillars with a constant cross-sectional area, leads to excessive deformation of the center pillar under collision loads due to the moment input, necessitating reinforcement to achieve desired load-bearing capabilities.
Innovation Solution
The vehicle structure body features roof side rails with a reduced cross-sectional area from the front of the center pillar toward the rear, allowing for controlled deformation and reduced moment input to the center pillar, enabling the structure to change shape under load while minimizing reinforcement needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cross-sectional area of the roof side rail is maintained constant, then the structural strength is improved, but the deformation of the center pillar increases under collision loads
Solution Approach 1:
The patent applies local quality by varying the cross-sectional area of the roof side rail along its length. Specifically, the cross-sectional area is reduced from the front of the center pillar toward the rear end of the roof side rail, creating different structural properties in different locations. This allows the front portion to maintain high strength while the rear portion provides flexibility to reduce moment input to the center pillar during collision.
Solution Approach 2:
The patent implements parameter changes by modifying the cross-sectional area parameter of the roof side rail. The cross-sectional area is continuously reduced over a predetermined length from the front of the center pillar toward the rear end, transforming the rigid constant-cross-section structure into a variable-cross-section structure that can adapt its mechanical properties along the length to balance strength and deformation control.
2Stability of the object's composition
If the cross-sectional area of the roof side rail is reduced from the front of the center pillar toward the rear end, then the center pillar deformation is suppressed, but the structural strength may be compromised
Solution Approach 1:
The reduction in cross-sectional area is applied locally and selectively - specifically from the front of the center pillar toward the rear end, while maintaining adequate cross-sectional area at critical load-bearing locations. This localized modification allows the structure to achieve desired deformation characteristics without compromising overall structural strength.
Solution Approach 2:
The cross-sectional area is reduced only over a predetermined length from the front of the center pillar, rather than throughout the entire length of the roof side rail. This partial action approach ensures that the reduction in moment input to the center pillar is achieved without excessively compromising the structural strength where full cross-sectional area is maintained.
3Strength
If the cross-sectional area is continuously reduced over a predetermined length, then the structural strength reduction is suppressed, but the manufacturing complexity increases
Solution Approach 1:
The continuous reduction of cross-sectional area over a predetermined length provides a gradual transition rather than abrupt changes, which can be achieved through standard manufacturing processes such as gradual forming or progressive material removal. This approach balances the need to maintain structural strength with manufacturability constraints.
Data Source
AI summary
A vehicle structure body includes roof side rails 10 that extend in the longitudinal direction of a vehicle on both sides in a vehicle width direction, and center pillars 20 that are connected to rear end portions 10a of the roof side rails 10 and extend in a vertical direction of the vehicle. The cross-sectional area of the roof side rail 10 is substantially constant from the front end of the roof side rail 10 to a front position P in front of the center pillar 20, and the cross-sectional area of the roof side rail is reduced from the front position P to a position S immediately before a joint portion between the roof side rail 10 and the center pillar 20. When a collision load acts on the roof side rail 10, the roof side rail 10 is easily folded at a portion of which the cross-sectional area is reduced. Accordingly, it is possible to reduce the input of moment to the center pillar 20.