Vehicle Joining Member Stiffness Weight Trade-off
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Solution Overview
Problem
Existing vehicle joining members increase weight while attempting to enhance stiffness, which hinders lightweight vehicle design.
Innovation Solution
A joining member configuration with an upper and lower fastening surface, where the instrument panel reinforcement is held between them, and a coupling portion that contacts the outer circumferential surface, reducing the length of the force transmission path and allowing for a lighter weight structure without covering the entire circumference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bracket is formed so as to surround the instrument panel reinforcement with the attachment surface and the bent surface in order to obtain stiffness, then the stiffness is improved, but the weight of the bracket increases
Solution Approach 1:
The joining member covers only a part of the outer circumferential surface of the instrument panel reinforcement in the circumferential direction, rather than covering the entire circumference. This partial coverage is sufficient to achieve the required stiffness while significantly reducing the amount of material needed, thereby preventing weight increase.
Solution Approach 2:
The joining member is configured with varying coverage along the circumferential direction, providing enhanced stiffness where needed (near the fastening holes) while reducing material in other areas. This localized quality distribution optimizes the stiffness-to-weight ratio.
2Strength
If the joining member covers the entirety of the outer circumferential surface in the circumferential direction, then the stiffness is improved, but the weight increases
Solution Approach 1:
The joining member is designed to cover only a portion of the outer circumferential surface rather than the entire circumference. This partial coverage provides sufficient stiffness for the application while using less material, thus avoiding weight increase.
3Stability of the object's composition
If the distance from the center axis to the imaginary plane connecting the fastening surfaces is increased, then the structural stability is improved, but the length of the force transmission path increases, reducing stiffness
Solution Approach 1:
The fastening holes are positioned in advance close to the instrument panel reinforcement, and the joining member geometry is designed to minimize the distance from the center axis to the imaginary plane connecting the fastening surfaces. This preliminary optimization of the force transmission path ensures short stiffness-critical paths while maintaining structural stability.
Data Source
AI summary
A first joining member configured to be used to join an instrument panel reinforcement to a vehicle body includes upper and lower body fastening surfaces to be fastened to the vehicle body. The first joining member is configured to be able to hold the instrument panel reinforcement between the upper and lower body fastening surfaces. There is defined an imaginary line that is orthogonal to an imaginary plane connecting the upper and lower body fastening surfaces, and passes through a center axis, extending in a vehicle-width direction, of the instrument panel reinforcement held by the first joining member. A distance along the imaginary line from the center axis to the imaginary plane is equal to or shorter than a distance along the imaginary line from the center axis to an outer circumferential surface of the instrument panel reinforcement.