Partitioned Side Sill Structure for EV Battery Side Impact
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Solution Overview
Problem
Existing side sill structures in automotive bodies, particularly in battery-powered vehicles, face challenges in achieving high impact energy absorption with minimal deformation while maintaining a lightweight design, and often result in excessive weight or inadequate protection of the battery module during side impacts.
Innovation Solution
A side sill structure incorporating a partition member that vertically passes through a closed sectional space, with a specific impact absorbing structure featuring sectionally groove-shaped members and bulkheads strategically positioned to absorb impact energy while minimizing weight and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a member with high rigidity and high proof stress is used for the battery case, then the battery cell is protected from impact load, but the weight of the structure increases
Solution Approach 1:
The patent changes the material parameter by using aluminum alloy (specifically Al-Mg-Si系 alloy) for the side sill instead of traditional high-strength steel. This parameter change allows achieving sufficient impact resistance while reducing weight, as aluminum alloy has a higher strength-to-weight ratio compared to conventional materials used in side sills
Solution Approach 2:
The patent employs composite material strategy by combining aluminum alloy side sill with steel battery case and floor cross member. This composite approach allows each component to be made from the most suitable material for its specific function, optimizing both weight and strength characteristics of the overall structure
2Volume of moving object
If the amount of deformation required for energy absorption of the side sill is reduced, then the energy absorbing portion can be reduced and battery module volume can be expanded, but the impact energy absorption capability may be compromised
Solution Approach 1:
The patent changes the material parameter to aluminum alloy with specific tensile strength requirements (270 MPa or more, preferably 310 MPa or more). This parameter change enables the side sill to achieve higher specific strength, allowing reduced deformation volume while maintaining energy absorption capability through material properties rather than structural volume
Solution Approach 2:
The patent applies local quality principle by designing the side sill with specific structural features including a lower flange portion with predetermined cross-sectional area and positioning the bulkhead at specific locations. These local structural optimizations ensure efficient energy absorption in critical areas while minimizing overall deformation volume
3Stability of the object's composition
If multiple bulkheads are disposed in the closed sectional space of the side sill, then cross-section collapsing is prevented at the time of side impact, but the weight and complexity of the structure increases
Solution Approach 1:
The patent applies partial action principle by disposing only one bulkhead in the closed sectional space of the side sill, rather than multiple bulkheads. This single bulkhead is strategically positioned to provide sufficient cross-section stability during side impact while avoiding the unnecessary weight and complexity of multiple bulkheads
Solution Approach 2:
The patent changes the structural parameter by optimizing the bulkhead's position and dimensions, and the lower flange portion's cross-sectional area. These parameter optimizations allow a single bulkhead to achieve the same stabilizing effect that would require multiple bulkheads in conventional designs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed structure achieves high impact energy absorption with reduced deformation and weight, effectively protecting the battery module by distributing impact loads efficiently across the side sill and floor cross member.
Implementation Method 1
a member having a function of absorbing energy by deformation of the member itself is disposed around the battery case
Implementation Method 2
the side sill absorbs energy of an impact load from the side of the automotive body
Data Source
AI summary
A lower structure of automotive body of an automobile includes: side sills arranged on both sides of an automotive body lower portion along a vehicle longitudinal direction; a floor cross member arranged between the side sills and having both side portions fixed to upper portions of the side sills; and a battery case arranged below the floor cross member and having both side portions facing lower portions of the side sills. Each of the side sills includes: a partition member that vertically passes a closed sectional space in the side sill, and has a structure in which the closed sectional space is partitioned into a first closed sectional space and a second closed sectional space in a vehicle width direction by the partition member; and an impact absorbing structure.