Rotor Permanent Magnet Segmentation for Dynamo-Electric Machines
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Solution Overview
Problem
In dynamo-electric machines with rotors using permanent magnets, manufacturing tolerances and temperature-induced expansion/contraction lead to gaps and stress concentration, causing damage, while existing designs either form gaps or increase warping risks, and manufacturing costs.
Innovation Solution
A rotor design with permanently magnets intermittently arranged circumferentially, featuring primary and secondary contacting portions and non-contacting portions to minimize contact area, reduce stress concentration, and utilize a tubular cover for fixation without bonding agents, optimizing contact angles to reduce torque ripple and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If permanent magnets are configured into an arcuate form to reduce material usage, then the amount of permanent magnet material is reduced, but gaps form between the permanent magnet and rotor core due to manufacturing tolerance and thermal expansion/contraction, causing stress concentration and potential damage
Solution Approach 1:
The inner peripheral surface of the permanent magnet is segmented into multiple contact portions (first contact portion, second contact portion, third contact portion) rather than being a continuous arcuate surface. This segmentation allows the magnet to maintain reliable contact with the rotor core at multiple discrete locations, preventing gap formation while still using an arcuate overall shape that reduces material usage.
Solution Approach 2:
Different portions of the permanent magnet's inner peripheral surface have different functional qualities: the first, second, and third contact portions are designed to contact the rotor core for structural support and stress distribution, while other portions may have different geometries optimized for magnetic performance or manufacturing. This local differentiation resolves the contradiction between material reduction and reliability.
2Stability of the object's composition
If permanent magnets are configured into an arcuate form with two projections to limit deformation, then the deformation of permanent magnets is limited, but gaps still form between the circumferential center portion and rotor core, causing stress concentration
Solution Approach 1:
Instead of using only two projections, the invention segments the contact surface into three or more contact portions distributed around the permanent magnet. This additional segmentation provides more contact points with the rotor core, ensuring that the circumferential center portion maintains contact and avoiding stress concentration, while still allowing the magnet to expand and contract thermally without excessive deformation.
3Reliability
If permanent magnets are configured with a flat opposing surface to eliminate gaps, then gaps are not formed regardless of thermal expansion/contraction, but the surface area increases leading to higher warping risk and manufacturing costs
Solution Approach 1:
The invention uses an arcuate inner peripheral surface with specific curvature rather than a flat surface. This curved geometry naturally accommodates thermal expansion and contraction, maintaining contact with the rotor core through multiple discrete contact portions. The curvature is optimized to reduce the overall surface area compared to a flat design, thereby reducing warping risk and manufacturing cost while still eliminating harmful gaps.
4Quantity of substance
If permanent magnets are intermittently arranged in the circumferential direction to reduce material usage, then the total amount of permanent magnet material is reduced, but stress concentration occurs in the center portion when external force is applied
Solution Approach 1:
The permanent magnet design incorporates specific local features: multiple contact portions on the inner peripheral surface that contact the rotor core at strategically located positions. These contact portions act as stress distribution points, locally reinforcing the magnet structure against external forces. This allows the overall magnet volume to be reduced through intermittent arrangement while maintaining high stress resistance through optimized local contact geometry.
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
This design minimizes damage from external forces, reduces material usage, and simplifies manufacturing by distributing stress and eliminating the need for bonding agents, while maintaining performance and reducing cogging torque.
Implementation Method 1
a rotor 30 for a dynamo-electric machine
Implementation Method 2
the radius of curvature of the inner peripheral surface of the permanent magnet may be changed through expansion or contraction of the permanent magnet depending on a temperature change
Data Source
AI summary
Each permanent magnet provided in a rotor includes a projection that projects toward a corresponding predetermined portion of the rotor core. An inner peripheral surface of each permanent magnet, which is radially opposed to the corresponding predetermined portion of the rotor core, includes a primary contacting portion and two primary non-contacting portions. The primary contacting portion contacts the corresponding predetermined portion of the rotor core at a circumferential location, which corresponds to the projection. The primary non-contacting portions do not contact the rotor core and are located on two circumferentially opposite sides, respectively, of the primary contacting portion.