One-Piece Rear Frame Casting for Stiffness and Coating Drainage
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Solution Overview
Problem
The existing rear frames for electric vehicles face challenges in maintaining stiffness due to joint fractures and increased manufacturing complexity and cost, while also experiencing issues with electrodeposition coating solution stagnation during the manufacturing process.
Innovation Solution
A rear frame design that forms a unitary one-piece structure using a casting method, eliminating mechanical fasteners and reducing the number of components, and incorporating features such as through holes in recessed structures to prevent electrodeposition coating solution stagnation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mechanical fasteners (SPR, FDS) are used to join rear side members and crossmembers, then the rear frame can be assembled, but the stiffness of the vehicle rear structure is lost
Solution Approach 1:
The patent integrates multiple rear frame components (rear side members and crossmembers) into a single monolithic structure formed by one pressing operation, eliminating the need for mechanical fasteners and welding. This merging of components resolves the stiffness loss caused by joint fractures while reducing assembly complexity.
2Ease of manufacture
If multiple components are manufactured by pressing and joined using fasteners and welding, then the rear frame can be assembled, but the manufacturing process becomes very complex and manufacturing cost increases
Solution Approach 1:
The patent combines multiple pressing operations into a single pressing process that forms all rear frame components (rear side members and crossmembers) as one integrated structure. This eliminates subsequent joining operations (fastening, welding) and reduces the number of parts, thereby simplifying the manufacturing process and reducing costs.
3Ease of manufacture
If the rear frame is manufactured by casting method, then the number of parts and manufacturing cost are reduced, but the electrodeposition coating solution stagnates in the pocket structure during electrodeposition coating
Solution Approach 1:
Instead of having closed pocket structures that trap coating solution, the patent designs the recessed structures with open tops that allow coating solution to drain freely. This inverted approach to pocket structure design eliminates the harmful stagnation and burning effects while maintaining the manufacturing advantages of integrated forming.
4Strength
If closed cross sections are used for rear side members and crossmembers, then the target stiffness can be met, but the manufacturing process becomes complex and cost increases
Solution Approach 1:
The patent forms all rear frame components with their cross-sectional structures in a single pressing operation, achieving the required stiffness through the integrated monolithic structure rather than through complex multi-step manufacturing of separate closed-section components. This eliminates the need for subsequent joining operations.
Data Source
AI summary
An embodiment rear frame includes a pair of side portions spaced apart from each other in a width direction of a vehicle, a first cross portion connecting front portions of the side portions, and a second cross portion connecting rear portions of the side portions, wherein the side portions and the first and second cross portions together are a unitary one-piece structure, and wherein each side portion includes a front mounting surface on which a front mount of a rear subframe is mounted, a front recessed structure on the front mounting surface, a rear mounting surface on which a rear mount of the rear subframe is mounted, and a rear recessed structure on the rear mounting surface, the front and rear recessed structures each having a pocket shape with an open top and a through hole.