Suspension Subframe Fragile-Link Structure for Cabin Deformation Restraint
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Solution Overview
Problem
Existing vehicle suspension subframe structures face challenges in effectively restraining cabin deformation during impact loads from the front side while maintaining a lightweight design, as they either require rigid tower members that increase weight or rely on load paths that can cause cabin deformation due to unabsorbed impact loads.
Innovation Solution
A suspension subframe structure with a body and fixed portion connected via a fragile portion of lower strength, allowing the subframe to break and disengage from the vehicle body under high impact loads, thereby preventing cabin deformation and distributing loads through alternative paths when loads are smaller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tower member is made rigid to restrain bending deformation under impact load, then the shock absorbing function of the extension frame is ensured, but the vehicle weight increases
Solution Approach 1:
The connection portion is segmented into a fragile portion with lower strength than the body and fixed portion. This segmentation allows the structure to have different mechanical properties in different regions, enabling the fragile portion to break under impact load while the body maintains sufficient strength, thus resolving the contradiction between ensuring shock absorbing function and reducing vehicle weight.
Solution Approach 2:
The strength parameter of the connection portion is deliberately reduced by introducing a fragile portion with lower strength than the body and fixed portion. This parameter change allows the connection portion to fail in a controlled manner under impact load, enabling weight reduction while maintaining the shock absorbing function through the extension frame's deformation.
2Reliability
If the subframe is used as a load path with high rigidity in the front-rear direction, then the subframe can receive impact load from the extension frames, but deformation of the vehicle cabin may occur due to unabsorbed impact load being transmitted to the cabin
Solution Approach 1:
The connection portion is segmented into a fragile portion that acts as a controlled weak point. This segmentation allows the subframe to function as a load path during normal operation while providing a failure mode that prevents unabsorbed impact loads from being transmitted to the vehicle cabin, thus resolving the contradiction between load receiving function and preventing cabin deformation.
Solution Approach 2:
The fragile portion's lower strength is converted from a potential weakness into a beneficial feature. When impact load exceeds the absorption capacity of the extension frame, the fragile portion breaks, converting the harmful unabsorbed impact load into a controlled separation that prevents cabin deformation. The harmful factor (potential cabin deformation) is transformed into a protective mechanism.
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 effectively restrains cabin deformation by allowing the subframe to disengage under large impact loads, preventing load transmission to the cabin and maintaining a compact, lightweight design.
Implementation Method 1
a connection portion connecting the fixed portion to the body, and the connection portion is provided with a fragile portion having a lower strength against a load in a vehicle front-rear direction than the body and the fixed portion
Data Source
AI summary
Provided is a suspension subframe structure that can activate a load path using an extension frame in an impact while avoiding increase in vehicle weight and also enables a suspension subframe to disengage from a vehicle body when an impact load is too large to be absorbed by the extension frame alone. The suspension subframe structure of the present invention includes a suspension subframe 110 that supports a suspension member 60 for a front wheel. The suspension subframe 110 includes: a body 111 that transmits an impact load input from a vehicle front side toward a vehicle rear side; a fixed portion 124 disposed near the body 111 and fixed to a vehicle body; and a connection portion 121 connecting the fixed portion 124 to the body 111. The connection portion 121 is provided with fragile portions 121f, 122g having a lower strength against a load in a vehicle front-rear direction than the body 111 and the fixed portion 124.