Automotive Rear Subframe Segmentation for Rigidity and Stability
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Solution Overview
Problem
Conventional automotive rear vehicle body structures face challenges in achieving lighter weight and higher rigidity in the rear subframe while maintaining arm length and enhancing rear impact safety, due to issues with the distribution of rear impact loads and deformation during collisions.
Innovation Solution
The design includes right and left rear side frames with a vehicle-body cross member forming a closed cross-section, and a rear subframe with side member segments having rear and front fixing sections. The front fixing section of each side member segment is positioned inward of the rear side frames, with an arm support section positioned rearward to pivotally support suspension arms, allowing for improved load distribution and increased rigidity without additional reinforcing members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the side member segment is curved inwardly with a long distance between front and rear fixing sections to ensure installation space for suspension spring and increase arm length, then the suspension geometry stability is improved, but the rigidity against lateral force decreases and weight increases
Solution Approach 1:
The side member is divided into multiple segments (first side member segment, second side member segment, third side member segment) connected by joining sections. This segmentation allows each segment to be optimized for specific functions: the first segment provides arm length, the second segment ensures rigidity with shorter fixing section distance, and the third segment provides spring installation space. The joining sections transmit forces between segments to maintain overall structural integrity and rigidity.
Solution Approach 2:
Different portions of the side member structure are given different geometric characteristics tailored to local requirements. The first side member segment has a first curvature radius optimized for arm length, the second segment has a second curvature radius optimized for rigidity, and the third segment has a third curvature radius optimized for spring installation. This local optimization allows each region to perform its specific function efficiently without compromising overall performance.
2Strength
If the plate thickness of the side member segment is increased to ensure rigidity against lateral force, then the rigidity is improved, but the weight increases
Solution Approach 1:
The side member is segmented into multiple sections with different thickness optimizations. The first side member segment can have a first plate thickness optimized for its specific structural role, while the second side member segment has a second plate thickness optimized for rigidity requirements. This segmentation allows weight optimization in regions where full thickness is not required, while maintaining necessary rigidity in critical areas.
3Stability of the object's composition
If the distance between front fixing section and arm support section is increased to improve suspension geometry stability, then the arm length is increased, but the rigidity of the subframe decreases
Solution Approach 1:
The side member is divided into segments where the first side member segment provides the arm support function with appropriate length for suspension geometry stability, while the second side member segment provides structural reinforcement with shorter dimensions for rigidity. The joining section connects these segments and transmits forces between them, allowing the structure to achieve both long arm length for stability and sufficient rigidity through the combined segmented system.
4Area of stationary object
If the extension member length is increased to connect the side member to the vehicle-body cross member, then the installation space is increased, but the deformation resistance of the extension member decreases and weight increases
Solution Approach 1:
The extension member function is extracted and integrated directly into the side member structure. The second side member segment extends rearward to directly connect to the vehicle-body cross member, eliminating the need for a separate long extension member. This integration provides sufficient installation space while maintaining shorter, stiffer connection geometry that resists deformation and reduces weight.
Data Source
AI summary
Disclosed is an automotive rear vehicle body structure which comprises a rear subframe (21) provided with right and left side member segments (22). Each of the right and left side member segments (22) has a rear region provided with a rear fixing section (26) attached to a respective one of right and left rear side frames (7), and a front region provided with a front fixing section (25) attached to a vehicle-body cross member (10). A position of the front fixing section (25) of each of the side member segments (22) is set to be located inward of the respective one of the rear side frames (7) in a vehicle width direction, and each of the side member segments (22) is provided with an arm support section (28) configured to pivotally support a suspension arm (32), at a position rearward of the front fixing section (25).