Vehicle Sub Frame With Variable Cross-Section Side Member
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Solution Overview
Problem
Existing rear suspension sub frame structures in vehicles face challenges in balancing strength against longitudinal loads and effective collision load absorption during rear collisions, as improving strength for longitudinal loads can compromise the ability to absorb collision loads.
Innovation Solution
A sub frame structure with a pair of side members connected to rear wheels, a rear cross member, and a front cross member, where a weak portion is intentionally designed to be weaker than the rest, allowing it to deform and absorb collision loads while maintaining strength against longitudinal loads by transmitting these loads to the vehicle body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the side member's strength is improved to handle increased longitudinal load, then the strength against longitudinal load is improved, but the side member cannot serve as a collision-load absorbing member properly in vehicle rear collision
Solution Approach 1:
The side member is designed with non-uniform cross-sectional area along its length, creating different local strengths at different positions. The front portion (first region) has a larger cross-sectional area for strength, while the rear portion (second region) has a smaller cross-sectional area for controlled deformation during collision, resolving the contradiction between overall strength and localized energy absorption.
2Device complexity
If the trailing arm is omitted to simplify the suspension structure, then the device complexity is reduced, but the longitudinal load transmitted to the rear sub frame increases
Solution Approach 1:
The side member's cross-sectional area parameter is varied along its length to compensate for the increased longitudinal load. By making the first region (front portion) have a larger cross-sectional area than the second region (rear portion), the structure can handle the higher loads without the trailing arm while maintaining appropriate deformation characteristics.
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 sub frame structure effectively absorbs collision loads by deforming the weak portion and ensures stable transmission of longitudinal loads, preventing excessive weakness in the weak portion and maintaining structural integrity during vehicle rear collisions.
Implementation Method 1
the weak portion of the side member deform toward a vehicle forward side between the front cross member and the rear cross member
Data Source
AI summary
A sub frame structure of a vehicle comprises a pair of right-and-left side members, to which a pair of right-and-left uppers-side lower arms are connected, a rear cross member holding rear ends of the side members, and a front cross member interconnecting the side members and being positioned in front of the rear cross member, being spaced apart from the rear cross member. A front end of each of the side members is rigidly connected to a floor frame, the front cross member is joined to a front side member of each of the side members, and a rear side member is provided at a portion of each of the side members which is positioned in back of the front cross member. Herein, the rear side member is configured to be weaker than the front side member.