Electric Motor Rotor Lamination Boss Design for Offset Stacking
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Solution Overview
Problem
Traditional laminations for electric motors face challenges in precise packing and stability, especially when creating rotors with skew or helical slots, as the interference between bosses can disrupt the evenness of the offset angle, leading to deviations in slot development and electrical characteristics.
Innovation Solution
A lamination design featuring bosses with a reduced thickness at one end to allow for offset coupling without relief holes, enabling precise and stable stacking with a U- or V-shaped profile, allowing for controlled necking during manufacturing to maintain the desired offset angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional laminations are coupled using bosses with relief holes, then the laminations can be assembled, but the interference between bosses disrupts the evenness of the offset angle, leading to deviations in slot development
Solution Approach 1:
The boss structure is modified to have different thicknesses at different locations: a first portion with reduced thickness and a second portion with greater thickness. This local differentiation allows the first portion to accommodate offset coupling without interference, while the second portion maintains structural integrity and proper angular positioning, thereby ensuring even offset angles and accurate slot development throughout the lamination stack.
2Adaptability or versatility
If relief holes are provided in bosses for offset coupling, then laminations can be stacked with offset angles, but the holes reduce the ferromagnetic material volume and complicate manufacturing
Solution Approach 1:
Instead of creating through-holes that remove material throughout the boss, the invention locally reduces the thickness only at the first portion of the boss that participates in offset coupling. This localized material removal provides the necessary adaptability for offset stacking while preserving the maximum possible volume of ferromagnetic material in the remaining portions of the boss and lamination.
Solution Approach 2:
The invention extracts only the minimum necessary material from the boss - specifically at the first portion that requires offset accommodation - rather than removing material through relief holes that would affect the entire boss structure. This selective extraction maintains ferromagnetic material volume while enabling offset coupling functionality.
3Length of stationary object
If the number of laminations in the pack increases, then the desired height is achieved, but the offset angle between adjoining laminations becomes smaller, making even distribution of offset angles more difficult
Solution Approach 1:
The differentiated boss structure with reduced thickness at the first portion enables each lamination to be precisely positioned relative to its neighbors regardless of the total pack height. The local geometric modification at the coupling interface ensures that even when the offset angle becomes very small in tall packs, the reduced thickness provides sufficient clearance to maintain consistent angular relationships across all laminations in the stack.
Data Source
AI summary
A method for manufacturing a lamination for electro motor rotors that have skew or helical slots by forming at least one boss on a face of the lamination and reducing a thickness of a first portion of the boss. The reduction in thickness may be by carrying out a localized narrowing of the thickness of the first portion and the boss may be manufactured by pressing the lamination. The localized narrowing may be carried out by misalignment of a die relative to a punch within a mould.