Battery Cover and Crossmember Layout for EV Underbody Impact Loads
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Solution Overview
Problem
Existing vehicle body lower section structures require large and heavy cross members to protect batteries from impact loads, leading to increased weight and size of the reinforcing structure.
Innovation Solution
A vehicle body lower section structure with a battery cover made of metal, connected to the front and rear cross members, which distributes impact loads efficiently across the vehicle, reducing the size and weight of the reinforcing structure by using a widened portion on the front cross member and a battery cover with reinforcing beads and ridges to manage stress and load transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large and strong cross members are used to protect the battery from impact loads, then the battery protection reliability is improved, but the weight and size of the vehicle body structure increase
Solution Approach 1:
The front cross member is segmented into different regions: a center region with smaller cross-sectional dimensions and widened portions at the end portions with larger cross-sectional dimensions. This segmentation allows each region to be optimized for its specific function, reducing overall weight while maintaining protection capability.
Solution Approach 2:
Different regions of the front cross member have different cross-sectional dimensions tailored to local requirements. The center region has smaller dimensions since it doesn't directly bear impact loads, while the widened portions at the end portions have larger dimensions to handle impact loads effectively. This local quality optimization reduces unnecessary material usage.
2Reliability
If large and strong cross members are used to protect the battery from impact loads, then the battery protection reliability is improved, but the size of the reinforcing structure increases
Solution Approach 1:
The front cross member is divided into a center region and widened portions at the end portions. This segmentation allows the structure to have smaller volume in the center region where full strength is not needed, while concentrating material in the widened portions that directly engage with the battery cover for impact protection.
Solution Approach 2:
The cross-sectional dimensions of the front cross member vary locally: smaller in the center region and larger in the widened portions at the end portions. This local quality approach ensures that material is only present where structurally necessary, minimizing the overall volume of the reinforcing structure while maintaining adequate protection.
3Weight of moving object
If the front cross member has a small cross-sectional area to reduce weight, then the vehicle body weight is reduced, but the impact load transmission capability deteriorates
Solution Approach 1:
The front cross member implements local quality by having different cross-sectional dimensions in different regions. The center region has smaller dimensions to reduce weight, while the widened portions at the end portions have larger dimensions specifically where impact load transmission is required, maintaining force transmission capability without excessive weight.
Solution Approach 2:
The front cross member features widened portions that expand in the vehicle width direction from the center region. This dimensional change allows the structure to have compact volume overall while providing localized areas of increased cross-sectional area for effective impact load transmission at the end portions.
Data Source
AI summary
A vehicle body includes: a vehicle body floor having a battery housing portion; a pair of left and right side sills; a front cross member disposed in front of the battery housing portion; a rear cross member disposed behind the battery housing portion; and a battery cover that covers a battery from above. A widened portion of which a height in a vertical direction increases with respect to a center region of the front cross member in a vehicle width direction and of which a front-rear width expands to a vehicle rear side with respect to a front-rear width of the center region of the front cross member in the vehicle width direction is provided on an end portion of the front cross member on an outer side in the vehicle width direction. The battery cover is made of a metal and includes an outer connecting portion connected to the widened portion on an outer side in the vehicle width direction.