Vehicle Lower Structure for Controlled Floor Cross Member Folding
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Solution Overview
Problem
Existing vehicle structures fail to effectively control the folding position of the floor cross member during a side collision, leading to potential damage to the floor panel.
Innovation Solution
A vehicle lower structure incorporating a rocker, floor cross member, gusset, and seat bracket, where the seat bracket has a low-strength portion and the floor cross member has a strength reduced portion, allowing controlled deformation to absorb impact energy and reduce panel damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the floor cross member is made strong to improve structural integrity, then the strength increases, but the folding position cannot be controlled during side collision causing floor panel damage
Solution Approach 1:
The floor cross member is designed with non-uniform strength distribution: a strength reduced portion is created at a specific location while other portions maintain full strength. This allows the member to be strong overall yet have a controlled weak point that dictates the folding position during side collision, preventing uncontrolled deformation that would damage the floor panel.
Solution Approach 2:
The floor cross member is segmented into different strength zones: a strong portion and a strength reduced portion. This segmentation allows different parts of the same member to serve different functions - the strong portion provides overall structural integrity while the strength reduced portion controls the deformation behavior during impact.
2Loss of energy
If the floor cross member is designed to deform freely to absorb impact energy, then energy absorption improves, but the folding position becomes uncontrolled causing floor panel breakage
Solution Approach 1:
By creating a localized strength reduced portion in the floor cross member, the deformation is guided to occur at a specific location away from the floor panel connection. This allows the member to deform and absorb impact energy while maintaining control over the folding position, preventing the uncontrolled deformation that would otherwise cause floor panel breakage.
3Strength
If the seat bracket is made strong to support the seat, then load bearing capacity increases, but it prevents controlled deformation of the floor cross member during collision
Solution Approach 1:
The seat bracket is designed with a localized low-strength portion at its center in the longitudinal direction. This allows the bracket to maintain high strength at its ends for supporting the seat and transmitting loads, while the low-strength portion at the center allows controlled deformation to occur, enabling the floor cross member to fold at the intended position during collision.
Solution Approach 2:
The seat bracket is segmented into strong end portions for load bearing and a weak central portion for controlled deformation. This segmentation allows the same component to fulfill dual functions: supporting the seat structure while enabling controlled energy absorption through deformation at the low-strength portion.
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 controls the folding position of the floor cross member, reducing the deformation amount of the floor panel and effectively absorbing impact energy during a side collision.
Implementation Method 1
the seat bracket is bent downward with the low-strength portion as a bending starting point, and the floor cross member is bent downward with the strength reduced portion provided at a position corresponding to the low-strength portion as a starting point
Implementation Method 2
a downward force is transmitted from the gusset to the strength reduced portion at the time of a side collision
Data Source
AI summary
The vehicle lower structure includes a rocker, a floor cross member, a gusset, and a seat bracket. The seat bracket is an elongated member extending in the vehicle width direction, and a low-strength portion is provided at the center in the longitudinal direction. The floor cross member is provided with a strength reduced portion at a position corresponding to the low-strength portion. The pressing flange on the vehicle width direction inner side of the gusset is connected to the side end portion of the floor cross member so as to overlap the strength reduced portion.