Electric Vehicle Subframe Z-Profile Welding
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Solution Overview
Problem
Conventional subframes for electric vehicles are inadequate in terms of stability and rigidity due to high mechanical stresses at welded seam connections, leading to potential component failure under the high torque and weight demands of electric motors.
Innovation Solution
A subframe design featuring a longitudinal member with Z-shaped sheet metal sections and strategically placed weld seams to minimize stress, combined with a wishbone connection system that reduces the number of welds and incorporates standing wishbone bearings to enhance rigidity and strength without significant weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional welded subframes are used for electric vehicles, then manufacturing simplicity is maintained, but stability and rigidity deteriorate under high torque conditions
Solution Approach 1:
The subframe is divided into multiple shell elements (first shell element, second shell element, third shell element) that are connected through defined connection regions. This segmentation allows each element to be optimized independently while maintaining overall structural integrity, resolving the contradiction by enabling complex geometries that enhance rigidity without requiring extensive welding throughout the entire structure.
Solution Approach 2:
The bearing section integrates multiple functions into a single structured opening that combines wishbone connection points, motor mounting points, and structural reinforcement into one unified component. This merging eliminates the need for separate welded brackets and attachments, thereby improving rigidity while reducing the number of welded connections that could compromise stability.
2Strength
If the number of welded connections is increased to improve strength, then connection strength improves, but the risk of component failure at weld seams increases
Solution Approach 1:
The structure is segmented into shell elements connected through defined connection regions that use minimal welding. The bearing section is integrated into the first shell element, eliminating the need for separate welded bearing brackets. This segmentation strategy maintains connection strength while reducing the total number of welded joints, thereby lowering the probability of weld-related failures.
Solution Approach 2:
The second shell element acts as an intermediary component that connects the first shell element (containing the bearing section) to the third shell element. This intermediary structure provides load paths that distribute stresses away from welded connections, maintaining connection strength while reducing reliance on numerous welds, thus lowering component failure risk.
3Reliability
If subframe weight is increased to improve stability, then stability improves, but vehicle weight increases leading to higher chassis wear
Solution Approach 1:
The subframe employs local quality optimization by concentrating material only where structurally necessary. The first shell element contains the bearing section with integrated connection points, providing localized reinforcement at high-stress areas. The second and third shell elements provide structural continuity with minimized material usage. This localized reinforcement achieves the required stability without uniformly increasing the entire subframe weight, thereby avoiding excessive vehicle weight increase.
Solution Approach 2:
The subframe utilizes composite construction with multiple shell elements made from sheet metal that are joined through defined connection regions. This composite approach allows optimization of each element's material properties and thickness locally, achieving high stability with minimized overall weight. The structured openings and integrated bearing sections provide high strength-to-weight ratio, ensuring stability without significant vehicle weight penalty.
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 design achieves higher flexural strength and rigidity while maintaining or slightly increasing weight, reducing mechanical stresses and potential for component failure, thereby ensuring stable operation under high torque conditions.
Implementation Method 1
The second single-shell metal sheet is connected to the first single-shell metal sheet by means of a weld seam
Data Source
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AI summary
The invention relates to a subframe (1) for a vehicle, in particular an electric vehicle, with a longitudinal member (2) composed of metal sheets, which has bearing connection points (9.1, 9.2) for a control arm connection, wherein the bearing connection points are formed in a bearing section (10) of the longitudinal member open towards the wheel carrier side, wherein the bearing section (10) is formed from a first single-shell metal sheet (2.1) and a second single-shell metal sheet (2.2), wherein the second single-shell metal sheet is connected to the first single-shell metal sheet by means of a weld (11), wherein the first single-shell metal sheet has at least one of the bearing connection points and wherein the second single-shell metal sheet has at least one of the bearing connection points.In order to achieve significantly higher stability, in particular higher bending strength and/or stiffness, of the subframe with the same or only slightly increased weight, the invention provides that the first single-shell metal sheet (2.1) has, in cross-section, a substantially z-profile-shaped shell section (2.11) which has a profile section (2.111) facing the wheel carrier side, a profile section (2.113) facing away from the wheel carrier side, and a profile section (2.112) which integrally connects the two profile sections and is substantially upright in the assembled state of the subframe (1), wherein the weld seam (11) is arranged at a distance (A) from the substantially upright profile section (2.112) on the profile section (2.113) facing away from the wheel carrier side.