Vehicle Rear Floor Structure for Offset Impact Load Dispersion
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Solution Overview
Problem
Existing hybrid electric vehicles, particularly plug-in hybrid electric vehicles, face challenges in effectively protecting the fuel tank and battery from rear-end collisions, especially during offset impacts, where the rear cross member deforms and fractures, leading to insufficient impact dispersion and potential damage.
Innovation Solution
A rear structure for vehicles featuring a cross member, side extensions, diagonal members, and reinforcing members that distribute collision energy, allowing for a single high-voltage battery to be water-cooled and the fuel tank to be positioned closer to the rear, with a design that enhances impact absorption and minimizes deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional rear structure with a back beam and rear cross member is used, then the structure is simple to manufacture, but the impact dispersion is insufficient during offset collisions causing the back beam to deform and fracture
Solution Approach 1:
The rear structure is divided into multiple functional members: a back beam for initial impact absorption, rear cross members for lateral support, and diagonal members extending from the rear cross members to side members for optimized load distribution. This segmentation allows each component to perform its specific function effectively, preventing the back beam from fracturing under offset collision forces.
Solution Approach 2:
Diagonal members are introduced that extend obliquely from the rear cross members to the side members, creating a three-dimensional load path. This diagonal arrangement adds a new dimension to the force distribution, enabling more effective dispersion of impact forces during offset collisions compared to conventional horizontal-only structures.
2Volume of moving object
If the fuel tank is positioned closer to the rear to optimize space, then the space utilization is improved, but the protection against rear-end collisions becomes insufficient
Solution Approach 1:
The rear structure members (back beam, rear cross members, and diagonal members) are designed to absorb and dissipate collision energy before it can reach the fuel tank and battery. This pre-cushioning effect protects these components even when positioned closer to the rear for optimized space utilization.
Solution Approach 2:
The diagonal members act as intermediary elements between the rear cross members and side members, creating an additional protective barrier that helps distribute and reduce the force transmitted to the fuel tank during rear-end collisions.
3Quantity of substance
If batteries are disposed as two separate batteries to secure capacity, then the battery capacity is sufficient, but the impact protection for each battery is reduced
Solution Approach 1:
The battery system is segmented into two separate batteries positioned on the rear floor, allowing each battery to be independently protected by the rear structure. The diagonal members and rear cross members create protective zones around each battery location.
Solution Approach 2:
The rear structure provides localized protection at specific battery positions through the strategic placement of diagonal members and rear cross members, ensuring each battery location has adequate impact resistance while maintaining the segmented configuration for sufficient total capacity.
4Ease of manufacture
If the back beam is designed to be simple in structure, then the manufacturing is easy, but the deformation and fracture during offset impact cannot be suppressed
Solution Approach 1:
Instead of making the back beam alone more complex, the structure is segmented by adding separate rear cross members and diagonal members that work together to prevent back beam fracture during offset impacts.
Solution Approach 2:
Rear cross members and diagonal members serve as intermediary structural elements that transfer and distribute impact forces away from the back beam, reducing the stress on the back beam while maintaining its relatively simple manufacturing design.
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 rear structure effectively disperses collision energy, providing enhanced protection for both the battery and fuel tank, ensuring stable buckling and consistent member behavior during collisions, thereby improving the vehicle's rear collision performance.
Implementation Method 1
To evaluate a rear impact performance of a vehicle, an offset impact test laterally offset with respect to the longitudinal centerline of the vehicle is used. In this example, when a rear impact occurs, a back beam is deformed and fractured.
Implementation Method 2
when a rear impact occurs, a back beam is deformed and fractured. Although additional deformation is suppressed by a rear cross member
Data Source
AI summary
A rear structure of a vehicle includes: a rear floor, and a pair of diagonal members coupled to a bottom surface of the rear floor, extending obliquely from both sides of the rear floor to a rear side of the rear floor, and symmetrical with respect to a longitudinal centerline of the rear floor. The rear structure further includes a pair of side extensions coupled to the bottom surface of the rear floor at the both sides of the rear floor, respectively, and extending in a longitudinal direction of the rear floor. The rear structure includes a cross member disposed between the pair of side extensions at a rear bottom surface of the rear floor, and the cross member has both ends each spaced apart from a corresponding side extension.