Vehicle Sub Frame Torsional Rigidity via 3D Upper Members
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Solution Overview
Problem
The existing multi-link type rear suspension systems in vehicles face issues with deformation and twisting of the sub frame due to uneven road surfaces, leading to increased vibrations, noises, and reduced maneuverability and stability.
Innovation Solution
A sub frame structure with a pair of right-and-left side members configured such that the distance between their rear ends is smaller than the distance between their front ends, featuring a rear cross member and a front cross member interconnected by an upper member, which disperses loads and restricts vertical movement to enhance torsional rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multi-link type rear suspension is used, then the suspension can effectively absorb vertical loads and suppress impacts, but the longitudinal load transmitted to the rear sub frame increases, causing deformation and twisting of the side member
Solution Approach 1:
The sub frame is transformed from a planar structure to a three-dimensional structure by adding upper members that connect the front and rear cross members in the vehicle longitudinal direction at positions above the side members. This dimensional change creates a spatial framework that significantly enhances torsional rigidity and suppresses deformation of the side members under longitudinal loads while maintaining suspension functionality
2Device complexity
If the trailing arm is omitted to simplify the suspension structure, then device complexity is reduced, but the longitudinal load on the rear sub frame increases, leading to improper deformation and twisting
Solution Approach 1:
By elevating the connection between front and rear cross members into the third dimension through upper members positioned above the side members, the structure gains enhanced torsional stiffness. This three-dimensional configuration provides sufficient structural stability even when the trailing arm is omitted, allowing for a simpler suspension design without compromising sub frame integrity
3Ease of manufacture
If the sub frame structure is simplified, then ease of manufacture is improved, but torsional rigidity decreases, causing increased vibrations and noises
Solution Approach 1:
The upper members connect the front and rear cross members in the vertical plane, creating a three-dimensional sub frame structure. This spatial configuration significantly increases torsional rigidity, effectively suppressing vibrations and noises from road inputs, while the modular design with clearly defined connection points maintains ease of manufacture and assembly
Data Source
AI summary
A sub frame structure of a vehicle comprising a pair of side members with front ends rigidly connected to a floor frame, a rear cross member holding the vicinity of rear ends of the side members, both-side end portions of which are rigidly connected to a rear side frame, the both-side end portions of the rear cross member being positioned on an outward side, in a vehicle width direction, of the side members, a front cross member interconnecting the side members in the vehicle width direction and being positioned in front of the rear cross member, being spaced apart from the rear cross member, and a pair of upper members respectively connecting an upper portion of the rear cross member and an upper portion of the front cross member in a vehicle longitudinal direction at a position above the side member.