Prestressed Fiber Split Cage for EV Traction Motor Gap Stability
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Solution Overview
Problem
Electric motor vehicle traction motors with liquid-cooled stators and dry-running rotors face mechanical sensitivity due to deformations in fiber composite split cages, which affect their mechanical robustness and electrical efficiency.
Innovation Solution
A fiber composite split cage is axially prestressed using a split cage axial stressing apparatus, providing long-lasting rigidity and resistance to radial forces, allowing for a thin-walled design with precise manufacturing and improved assembly efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fiber composite split cage is used to achieve thin-walled design and high electrical efficiency, then the radial gap between stator and rotor is reduced, but the mechanical robustness deteriorates due to sensitivity to deformations under radial forces
Solution Approach 1:
The split cage is axially prestressed during assembly using a stressing apparatus that applies compressive force through the end plates. This preliminary action creates initial compressive stress in the fiber composite body that counteracts the tensile deformations caused by radial centrifugal forces during motor operation, preventing deformation and maintaining mechanical robustness while enabling thin-walled design
Solution Approach 2:
The axial prestress changes the stress state parameters of the fiber composite split cage from purely tensile to a combined compressive-tensile state. By adjusting the prestress magnitude, the cage can withstand radial forces without exceeding material strength limits, thereby improving mechanical robustness while maintaining the thin-walled structure for high electrical efficiency
2Stability of the object's composition
If the split cage is made rigid enough to maintain shape outside installed state, then mechanical stability is improved, but the material thickness increases reducing electrical efficiency
Solution Approach 1:
The split cage is designed to be flexible during assembly but is pre-stressed into a rigid configuration once installed. The axial stressing apparatus applies compressive force that locks the cage into its final rigid shape, providing both ease of assembly and shape stability in operation without requiring excessive material thickness
Solution Approach 2:
The split cage transitions from a flexible state during assembly to a rigid state during operation. The axial prestress creates a dynamically stable structure that maintains its shape under operational loads while allowing for easier manufacturing and assembly with thinner walls, thereby improving both shape stability and electrical efficiency
Data Source
AI summary
An electric motor vehicle traction motor, including: a liquid-cooled motor stator, a dry-running motor rotor, and a fluid-tight split cage which separates the motor stator and the motor rotor from one another fluidically, the split cage being formed by a fiber composite body, wherein the split cage is axially prestressed in a long-lasting manner by a split cage axial stressing apparatus.