Automobile Side Sill Structure with Partitioned Energy Absorption

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Solution Overview

Problem

Existing side sill structures in automobiles fail to achieve sufficient collision energy absorption with minimal deformation and weight increase, particularly in battery electric vehicles, due to inefficient load transmission and excessive reinforcement in non-essential areas.

Innovation Solution

A side sill structure incorporating a vertical partition member and an impact absorption structural portion with horizontal partition members and bulkheads in a closed sectional space, optimized for efficient energy absorption and weight management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If a lightweight side sill structure is used to reduce weight, then weight is reduced, but collision energy absorption capability deteriorates

Engineering Contradiction:
Improveside sill weightVSAvoidcollision energy absorption capability
Core Design Contradiction:
Weight of moving objectVSStrength

Solution Approach 1:

The side sill is divided into multiple functional segments: a first closed section with high rigidity for load transmission, a second closed section with energy absorption members for controlled deformation, and a third closed section for structural continuity. This segmentation allows each portion to perform its specific function optimally, achieving high energy absorption with reduced overall weight.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The side sill employs composite construction combining different materials and structures: high-strength steel for the outer shell, energy absorption members made of deformable materials, and reinforced sections with rib structures. This composite approach enables the side sill to exhibit both high strength for load bearing and controlled deformability for energy absorption, resolving the contradiction between weight reduction and collision performance.

Inventive Principle:
Principle #40Composite materials

2Strength

If the deformation amount required for energy absorption is increased, then energy absorption capability is improved, but the volume of the battery module is reduced

Engineering Contradiction:
Improveenergy absorption capabilityVSAvoidbattery module volume
Core Design Contradiction:
StrengthVSVolume of moving object

Solution Approach 1:

The side sill cross-section is divided into multiple closed sections (first, second, and third closed sections) with different functions. The second closed section specifically contains energy absorption members that deform during collision, while the first and third sections maintain structural rigidity. This segmentation allows energy absorption to occur in a localized region without requiring overall structural deformation, thereby preserving battery module volume while achieving sufficient energy absorption capability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention introduces energy absorption members within the hollow interior space of the side sill's closed sections, utilizing the internal volume efficiently. By placing deformable elements inside the existing structural framework rather than increasing external dimensions, the design achieves enhanced energy absorption without encroaching on the battery module space, effectively using the third dimension (internal cavity space) to resolve the volume contradiction.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Strength

If reinforcing members are added to improve collision performance, then energy absorption capability is improved, but weight increases

Engineering Contradiction:
Improvecollision performanceVSAvoidside sill weight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

Rather than uniformly reinforcing the entire side sill, the invention segments the structure into distinct functional zones: high-rigidity sections for load transmission and localized energy absorption sections with controlled deformability. This targeted reinforcement approach minimizes the addition of heavy materials while maintaining collision performance through strategic placement of structural elements.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The side sill design incorporates dynamic characteristics by including energy absorption members that are designed to deform in a controlled manner during collision. Instead of using purely rigid reinforcing members throughout, the structure transitions from rigid (for load transmission) to deformable (for energy absorption) in specific regions, optimizing both performance and weight by allowing necessary deformation rather than over-reinforcing the entire structure.

Inventive Principle:
Principle #15Dynamics

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 structure achieves high collision energy absorption with minimal deformation and weight increase, allowing for expanded battery module volume and reduced energy absorption space, while maintaining crashworthiness.

Implementation Method 1

each of the horizontal partition members (5) has a bead (7) formed at a position between the bulkheads (6) along the vehicle width direction

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP4647325A1Side sill structure for automobile, and car underbody structure
Publication Date: 2025.11.12 JFE STEEL CORP
  • EP4647325A1 patent drawingFigure 1
  • EP4647325A1 patent drawingFigure 2
  • EP4647325A1 patent drawingFigure 3

AI summary

In a closed sectional space 3 in a side sill 1, an impact absorption structural portion 4 is provided using a vertical partition member 2 that vertically passes through the space. The impact absorption structural portion 4 includes a horizontal partition member 5 that traverses closed sectional spaces 3a and 3b on a vehicle body inner side and an outer side partitioned by the vertical partition member 2 in a vehicle width direction, and a bulkhead 6 provided along the vehicle width direction in upper spaces 30a and 30b partitioned by the horizontal partition member 5. The horizontal partition members 5 and the bulkheads 6 on the vehicle body inner side and the outer side are disposed to face each other with the vertical partition member 2 sandwiched therebetween, and beads are formed in the horizontal partition member 5 along the vehicle width direction. In this side sill structure, desired crash worthiness can be obtained even when the number of bulkheads 6 to be installed is reduced, so that a high collision energy absorption property can be obtained with a small collision deformation amount while suppressing an increase in weight due to a structural member.