Front Subframe Bent Portion Load Transfer Geometry
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Solution Overview
Problem
Existing front subframe structures face challenges in efficiently transferring collision loads during head-on collisions due to suboptimal design features, such as the shape of the lower arm and bent portion, which hinders reliable abutment and load transfer, affecting the detachment mechanism from the vehicle body.
Innovation Solution
A front subframe structure with a reinforced bent portion and improved load transfer paths, featuring a longitudinally extending arm and a reinforcing gusset that ensures parallel alignment between the rear face of the bent portion and the front face of the lower arm, enhancing load transferability and rigidity while maintaining a shape that circumvents the power train.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the subframe is shaped to circumvent the power train with the bent portion, joint portion, and forward projecting portion curving inward toward the vehicle width direction inner side, then the subframe can accommodate the power train layout and maintain structural flexibility, but the load transferability from the bent portion to the lower arm is reduced due to inability to create reliable abutment during collision
Solution Approach 1:
The patent applies preliminary action by pre-positioning the lower arm such that its front end is located at a position allowing direct contact with the bent portion's rear end face in the event of head-on collision. This preliminary positioning ensures that when collision occurs, the load can be immediately and reliably transferred from the bent portion to the lower arm without requiring complex abutment mechanisms, thus resolving the contradiction between shape adaptability and load transfer reliability.
2Shape
If the lower arm is shaped to incline further in the vehicle width direction inner side toward the rear side to circumvent the subframe, then the suspension geometry can be optimized for handling and packaging, but the abutment between the bent portion and lower arm becomes unreliable, reducing load transfer efficiency
Solution Approach 1:
The patent applies local quality by making the front end of the lower arm have a specific geometric configuration with a contact surface that is substantially perpendicular to the vehicle width direction. This localized geometric feature at the front end of the lower arm ensures reliable abutment with the bent portion during collision, while the rest of the lower arm can maintain its optimized suspension geometry that inclines toward the vehicle width direction inner side, thus resolving the contradiction between overall shape optimization and local abutment reliability.
3Strength
If the subframe is designed with high rigidity to support the suspension and power train during normal driving, then the structural strength is improved, but the ability to detach the subframe from the vehicle body during head-on collision is reduced due to the strong structure hindering deformation
Solution Approach 1:
The patent applies segmentation by dividing the subframe into distinct functional zones: the bent portion with reinforced load transfer paths for collision energy absorption and detachment, and other portions maintaining high rigidity for supporting the suspension and power train during normal driving. This segmentation allows different parts of the subframe to have different mechanical properties optimized for their specific functions, resolving the contradiction between overall rigidity and collision detachment capability.
Solution Approach 2:
The patent converts the harmful effect of high rigidity (which prevents necessary deformation during collision) into a benefit by designing specific load transfer paths that channel collision forces through designated areas. The reinforced bent portion and lower arm create controlled deformation zones that facilitate detachment, while the rest of the high-rigidity structure provides overall structural support, thus converting the potential harm of excessive rigidity into a beneficial controlled deformation mechanism.
Data Source
AI summary
A front subframe structure includes a subframe body and a pair of right and left longitudinal members. The subframe body includes an arm front-side supporting portion, an arm rear-side supporting portion, and a detaching portion. Each of the longitudinal members has, in the rear part thereof, a bent portion that is further in the vehicle width direction outer side with respect to the arm front-side supporting portion. A lower arm has, in the rear part thereof, a longitudinally extending portion. The rear face portion of the bent portion, and the front face portion which is in the front side of the longitudinally extending portion of the lower arm extend substantially parallel to each other along the vehicle width direction. A reinforcing portion is provided on a face of the rear face portion of the bent portion, the face opposing the front face portion of the longitudinally extending portion.