Vehicle Body Substructure with Underfloor Load Paths
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Solution Overview
Problem
Existing vehicle body substructures face challenges in protecting underfloor mounting components from lateral impact loads while maintaining boarding/alighting properties and controlling manufacturing costs, particularly in designs where the battery cross-member is prone to falling due to front-rear loads and where the battery pack's size is limited by its positioning below the side sills.
Innovation Solution
The vehicle body substructure incorporates side sill load transmitting members, a floor cross-member, underfloor mounting components with underfloor cross-members, and load transmitting members that disperse impact loads through multiple paths, allowing the floor and underfloor cross-members to absorb impacts without increasing side sill heights, and features a battery cross-member with hat-shaped side portion members for cost-effective manufacturing and enhanced rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If side sills are increased in height and energy absorption members are provided inside the side sills to protect the battery from lateral impact loads, then the battery protection is improved, but the boarding/alighting properties deteriorate and the side sill weight increases
Solution Approach 1:
The patent introduces a vertical dimension for load transmission by providing load transmitting members that extend from the floor cross-member downward to the underfloor cross-member. This creates a three-dimensional load path that transmits lateral impact loads vertically through the battery pack, protecting it without requiring increased side sill heights that would affect boarding/alighting.
2Reliability
If the battery pack is positioned below the side sills to protect it from lateral impacts, then the battery protection is improved, but the battery pack size is limited
Solution Approach 1:
The patent extends the load transmission path vertically by introducing underfloor cross-members and load transmitting members that connect the floor cross-member to the underfloor structure. This allows the battery pack to be positioned in the space below the floor panel while still receiving protection from lateral impacts through the vertical load path, thereby increasing the available volume for the battery pack.
3Reliability
If multiple load transmitting members are provided to disperse impact loads through multiple paths, then the battery protection is improved, but the device complexity increases
Solution Approach 1:
The patent segments the load transmission function into multiple independent paths: (1) direct transmission through the battery pack, (2) transmission through the floor cross-member to the underfloor cross-member via load transmitting members, and (3) transmission through the side sills. This segmentation allows the complex load dispersion function to be achieved through simple, modular structural elements that can be independently designed and manufactured.
4Ease of manufacture
If the battery cross-member is designed with hat-shaped side portion members for cost-effective manufacturing, then the manufacturing cost is reduced, but the rigidity may be compromised
Solution Approach 1:
The battery cross-member is constructed as a composite structure combining hat-shaped side portion members (which are cost-effective to manufacture) with a bottom portion member that provides additional rigidity. The combination of these different structural elements creates a composite cross-member that achieves both cost-effectiveness and sufficient rigidity for its protective function.
Data Source
AI summary
This vehicle body substructure includes side sill load transmitting members that are provided inside each of side sills, a floor cross-member that is provided on one of an upper surface and a lower surface of a floor panel laid between the side sills and has extending portions extending toward upper portions of the side sill load transmitting members, an underfloor mounting component that is provided below the floor panel and includes an underfloor cross-member, underfloor frames that are attached to lower portions of the underfloor mounting component and the side sills, and underfloor load transmitting members that are provided in the underfloor frames and face the underfloor cross-member. The underfloor load transmitting member has an upper half portion which faces a lower portion of the side sill load transmitting members, and a lower half portion which is fixed to a part of each of the underfloor frames attached to a lower portion of each of the side sills.