Vehicle Rear Structure with Closed Cross-Section for Collision Load Management
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Solution Overview
Problem
In vehicle rear portion structures, existing designs are prone to releasing the fixed state of the rear side member to the rocker due to collision loads from rear collisions, leading to stress concentration and potential instability.
Innovation Solution
A vehicle rear portion structure featuring a rocker and rear side member with a closed cross-section structural portion that extends in the longitudinal direction, interposed between the rocker and the rear side member, which absorbs collision loads and suppresses moments, and an inclined rocker portion that aligns with the rear side member's shear center to stabilize the structure during collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the front portion of the rear side member is curved toward the vehicle transverse direction outer side to achieve a wide opening width for welding, then the welding accessibility is improved, but a moment arises at the front portion during rear collision causing stress concentration and potential release of the fixed state
Solution Approach 1:
The front portion of the rear side member is divided into two functional zones: an inclined portion for welding accessibility and a curved portion for collision load management. This segmentation allows each zone to perform its specific function optimally without interfering with the other.
Solution Approach 2:
Different portions of the rear side member are given different geometric characteristics: the inclined portion has a gentle slope for welding access, while the curved portion has a specific curvature radius to control stress distribution during collision. Each local region is optimized for its specific function.
2Reliability
If the front portion of the rear side member is made straight to reduce moment during collision, then the structural stability during rear collision is improved, but the opening width for welding becomes narrow making welding difficult
Solution Approach 1:
The front portion is segmented into an inclined portion (for welding) and a curved portion (for collision resistance). This allows the structure to have both the straight geometry needed for stability and the geometry needed for welding access, by separating these functions into different segments.
Solution Approach 2:
The solution moves from a one-dimensional straight or curved geometry to a two-dimensional composite geometry with both inclined and curved portions. This dimensional complexity allows simultaneous optimization of welding accessibility and collision resistance.
3Weight of moving object
If the rocker inner panel is positioned closer to the rear side member to reduce structure weight, then the vehicle weight is reduced, but the space for welding gun insertion becomes limited
Solution Approach 1:
The inclined portion of the rear side member has a specific curvature radius that creates sufficient clearance space for welding gun insertion. This curved geometry allows the rocker inner panel to be positioned closer to the rear side member for weight reduction while maintaining adequate welding access space.
Data Source
AI summary
A vehicle rear portion structure has: a rocker disposed at a vehicle transverse direction outer side of a floor portion of a vehicle body, and extending in a vehicle longitudinal direction as seen from a vehicle vertical direction; a rear side member having a front portion, which is disposed at a vehicle transverse direction inner side of the rocker and is disposed at a position overlapping the rocker as seen from a vehicle transverse direction, and a rear portion, which extends from the front portion toward a vehicle rear side and extends in the vehicle longitudinal direction as seen from the vehicle vertical direction; and a closed cross-section structural portion that is structured to include a portion of the rocker and a portion of the front portion, that is interposed between the rocker and the front portion, and that extends in the vehicle longitudinal direction.