Vehicle Floor Cross Beam Widening Portion Side Impact Rigidity
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Solution Overview
Problem
Current vehicle body lower structures face challenges in achieving sufficient rigidity, particularly in All-Wheel Drive and Electric Vehicles, due to the inability to close the rear end of the floor tunnel and the increase in weight and components when using reinforcing members, which affects load dispersion and deformation in side collisions.
Innovation Solution
A vehicle body lower structure design featuring a floor cross beam with a widening portion that expands outward in the vehicle-width-direction, connected to the floor tunnel, which disperses and transfers the load to the floor tunnel and cross beam, enhancing rigidity and suppressing deformation during side collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reinforcing members such as stays are used to ensure the rigidity of the floor, then the rigidity of the floor is improved, but the number of components and the weight of the vehicle body will increase
Solution Approach 1:
The floor cross beam is segmented into an upper portion member and a lower portion member, forming a closed cross-section structure. This segmentation allows the structure to achieve higher rigidity through the closed section geometry rather than adding separate reinforcing members, thereby avoiding increased weight and component count.
Solution Approach 2:
The lower portion member includes a recessed portion with a widening portion that gradually expands outward in the vehicle-width-direction. This dimensional change creates a geometric reinforcement effect where the expanding cross-section provides structural strength without requiring additional reinforcing members, resolving the contradiction between rigidity and weight.
2Strength
If the rear end of the floor tunnel is sealed with the vertical wall of the floor cross beam, then the rigidity of the floor is improved, but the openings at the rear end of the floor tunnel cannot be closed in All-Wheel Drive and Electric Vehicles due to drive components and pipes
Solution Approach 1:
The floor cross beam is divided into upper and lower portion members, creating a closed cross-section structure that provides rigidity without requiring complete sealing of the floor tunnel openings. This segmentation allows the structure to maintain strength while accommodating drive components and pipes in AWD and EV vehicles.
Solution Approach 2:
The lower portion member features a localized recessed portion with a widening portion at the rear end, providing structural reinforcement exactly where needed rather than requiring complete sealing. This local quality approach maintains rigidity while allowing adaptability to different vehicle configurations with drive components.
3Strength
If the cross-sectional shape of the floor tunnel is modified to improve rigidity, then the rigidity in relation to left and right sidewalls load is improved, but the complexity of the structure increases
Solution Approach 1:
The lower portion member includes a recessed portion with a widening portion that gradually expands outward in the vehicle-width-direction. This dimensional change in the cross-sectional shape provides improved rigidity against sidewalls load while maintaining structural simplicity through a continuous geometric form rather than complex assembled components.
Data Source
AI summary
A vehicle body lower structure includes: a floor; lower longitudinal beams; a floor cross beam, connected to the lower longitudinal beams on outer sides in a vehicle-width-direction of the floor; and the floor cross beam includes an upper portion member and an lower portion member, where the upper portion member and the lower portion member form a closed cross-section; and a floor tunnel, connected to a center of the floor cross beam in the vehicle-width-direction, where the lower portion member is connected to an opened cross-section of the floor tunnel at a center in the vehicle-width-direction, and when looking up from a bottom portion of the vehicle body, the lower portion member has a recessed portion recessed toward an upper side of the vehicle body, and the recessed portion has an widening portion that gradually expands outward in the vehicle-width-direction toward a rear side of a vehicle.