EV Subframe Shell Structure With Spacer Tab Load Path
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Solution Overview
Problem
Conventional subframes for electric vehicles face stability issues due to high starting torques, leading to excessive bending stresses and potential failure of welds at connections, especially under dynamic axle loads.
Innovation Solution
The subframe incorporates a design with at least two shell elements and a bushing-like or sleeve-like spacer element, where the side wall of one shell element has a tab welded to the spacer element, creating an additional load path and enhancing stability without increasing weight significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sheet thickness of the sheet metal shells is increased to rule out component failure, then strength and stability are improved, but weight of the subframe increases considerably
Solution Approach 1:
The subframe is divided into two separate shell elements (first and second shell elements) that are rigidly connected to each other, creating a segmented structure. This segmentation allows each shell element to be optimized independently and distributes the load paths more effectively, improving strength without requiring uniform thickness increases throughout the entire structure.
Solution Approach 2:
A spacer element is introduced as an intermediary component between the first and second shell elements. This spacer element creates additional load paths and distributes stresses more effectively across the structure, enhancing strength and stability without requiring increased sheet thickness, thereby avoiding additional weight.
2Stability of the object's composition
If sheet thickness of the sheet metal shells is increased to prevent failure under high starting torques, then stability is improved, but material usage and weight increase
Solution Approach 1:
By segmenting the subframe into two rigidly connected shell elements, the structure achieves improved stability under high starting torques through better load distribution. Each shell element can be designed with optimal thickness, reducing overall material usage compared to a single thick-shell design.
Solution Approach 2:
The spacer element acts as a mediator that distributes the high starting torque loads across multiple load paths between the first and second shell elements. This intermediary structure enhances stability without requiring increased material usage, as the loads are spread throughout the assembled structure rather than concentrated in thicker individual shells.
3Weight of moving object
If conventional sheet metal elements are used with standard thickness, then weight is reduced, but the subframe fails due to excessive bending stresses in the transverse bridge connection area
Solution Approach 1:
The segmented structure with two rigidly connected shell elements creates additional load paths that distribute bending stresses away from the transverse bridge connection area. This allows the use of conventional sheet thicknesses while maintaining adequate strength, as the stresses are dispersed throughout the assembled structure rather than concentrated in single thick components.
Solution Approach 2:
The spacer element serves as an intermediary that provides additional structural support and load distribution pathways. It helps transfer and distribute bending stresses away from critical connection areas like the transverse bridge, enabling the use of lighter, conventional thickness sheet metal without sacrificing strength.
Data Source
AI summary
The invention relates to a subframe, in particular front axle subframe, for a vehicle, in particular electric vehicle, having a first shell element and a second shell element which is rigidly connected to the first shell element and defines a cavity therewith. At least one of the shell elements has a side wall which, as an outer wall of the subframe, is connected to the other shell element or to another of the shell elements in a materially bonded manner having at least one bushing-like or sleeve-like spacer element for the insertion of a fastening bolt, preferably a screw bolt, for connecting to a body or component. The spacer element is arranged at one of its ends at a through-hole of the first shell element and extending inside the cavity in the direction of a through-hole of the second shell element. In order for the subframe to provide greater stability, in particular improved safety against failure of weld seams at the body connection and/or component connection, e.g. transverse bridge connection, with less or only slightly increased weight, the invention provides that the side wall of the shell element has at least one tab which is welded to the spacer element. This allows at least one additional load path to be implemented in a direction parallel to the longitudinal center axis of the spacer element.