Vehicle Front Structure Subframe Drop Mechanism
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Solution Overview
Problem
The existing front structure of a vehicle body, as described in Patent Document 1, is not suitable for vehicles with a subframe arranged behind the engine, as it cannot smoothly drop the subframe downward when an impact load is applied from the front, leading to potential out-of-plane deformation and failure of the bolt fastening portion.
Innovation Solution
A front structure of a vehicle body configuration that includes a subframe with a tubular body and a convex portion protruding rearward, which is pressed against a fall restricting wall when an impact load is applied, restricting the falling of the tubular body and suppressing out-of-plane deformation of the support plate, allowing the subframe to drop downward smoothly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the subframe is bolted to a support plate with relatively low rigidity, then the subframe can be designed to drop downward upon impact, but the support plate may experience out-of-plane deformation causing the bolt fastening portion to fail to break smoothly
Solution Approach 1:
A convex portion is added as an intermediary element between the tubular body and the support plate. This convex portion acts as a mediator that concentrates the impact load onto a specific region of the support plate, ensuring reliable breaking of the bolt fastening portion while preventing out-of-plane deformation of the support plate itself.
Solution Approach 2:
The support plate is designed with non-uniform thickness, creating local quality variations. The plate has a first thickness in the region where the convex portion contacts it, and a second thickness elsewhere. This local variation in thickness allows the plate to break at the intended location (where the convex portion applies force) while maintaining sufficient rigidity in other areas to prevent out-of-plane deformation.
2Adaptability or versatility
If a support plate with relatively low rigidity is used to allow subframe dropping, then the subframe can fall downward upon impact, but the bolt fastening portion may not break smoothly due to out-of-plane deformation
Solution Approach 1:
The convex portion serves as a precision intermediary that directs the impact force to a specific, predetermined location on the support plate. This ensures that the bolt fastening portion breaks at the intended position with high precision, while still allowing the subframe to drop smoothly in response to impact.
Solution Approach 2:
The support plate's thickness parameter is varied spatially to achieve different mechanical properties in different regions. By changing the thickness from the first value (at the breaking location) to the second value (in other regions), the plate is designed to break precisely where needed while maintaining overall structural integrity and preventing unwanted deformation.
Data Source
AI summary
A front portion of a vehicle body includes front side frames, a subframe, and a vehicle compartment front structure body. The subframe has a subframe body and a pair of rear fastening portions fastened to a vehicle compartment front structure body in left and right rear regions of the subframe body. The rear fastening portion has a tubular body through which a bolt penetrates in a vertical direction, and a convex portion protruding from the tubular body toward a vehicle rear side. The vehicle compartment front structure body has a support plate extending substantially horizontally in which the tubular body is fastened to a lower surface of the support plate by the bolt, and a fall restricting wall facing the convex portion from the vehicle rear side at a position rearward of a fastening portion of the support plate fastened with the bolt.