Rotor Cover Contact Geometry for Press-Fitting Load Reduction
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Solution Overview
Problem
Existing rotor designs with consequent-pole structures face issues with insufficient holding force for permanent magnets due to manufacturing accuracy limitations, leading to potential damage and excessive press-fitting loads, which increase manufacturing costs and risk buckling during the press-fitting process.
Innovation Solution
A rotor design featuring a rotatable shaft, a rotor core with soft magnetic projections and arcuate permanent magnets, where the circumferential center portion of the projection's radially outer surface contacts the cover's inner surface, and the circumferential end portions are radially inwardly spaced, reducing the press-fitting load and ensuring a sufficient holding force while minimizing compressive stress on the magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the radially outer surface of each projection is designed to entirely contact the cover, then the holding force for permanent magnets is improved, but the press-fitting load becomes excessively large
Solution Approach 1:
The invention applies local quality by creating a chamfered portion at the radially outer surface of the projection, where only a specific region (the chamfered surface) contacts the cover during press-fitting. This localized contact area reduces the overall frictional resistance compared to entire surface contact, thereby reducing the press-fitting load while still providing sufficient holding force through the chamfered contact region.
Solution Approach 2:
The chamfered portion introduces a curved or angled surface geometry at the contact region. This curved surface design allows for more gradual stress distribution and reduced friction during the press-fitting process, enabling the cover to be fitted with lower load while maintaining adequate holding force for the permanent magnets.
2Force
If the radially outer surface of each projection entirely contacts the cover, then the holding force for permanent magnets is improved, but the frictional resistance becomes excessively large
Solution Approach 1:
By limiting the contact between the projection and cover to only the chamfered portion rather than the entire radially outer surface, the invention locally concentrates the functional contact area. This reduces the total frictional resistance during press-fitting while the chamfered geometry ensures sufficient holding force is generated at the contact interface.
Solution Approach 2:
The chamfered surface provides a curved contact interface that reduces frictional resistance compared to a flat radial surface. The angled or curved geometry of the chamfered portion facilitates easier fitting by distributing contact stresses and reducing the coefficient of friction during the press-fitting operation.
3Force
If the press-fitting load is increased to ensure full contact, then the holding force is improved, but the size of the press-fitting apparatus must be increased
Solution Approach 1:
The chamfered portion design allows the press-fitting operation to be performed with lower load by concentrating contact at the chamfered surface rather than requiring full radial surface contact. This reduces the required press-fitting apparatus capacity and simplifies the manufacturing equipment needed.
4Force
If the press-fitting load becomes excessive, then the holding force is ensured, but the manufacturing costs are increased
Solution Approach 1:
By designing the chamfered portion to provide the primary contact interface, the invention reduces the press-fitting load required compared to full radial surface contact designs. This lower load requirement translates to reduced manufacturing costs by enabling the use of smaller, less expensive press-fitting equipment and reducing the overall complexity of the manufacturing process.
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 achieves a balanced holding force for the permanent magnets, reduces the press-fitting load, and limits the risk of magnet damage, maintaining efficient motor performance while minimizing manufacturing costs and stress on the magnets.
Implementation Method 1
Each of the plurality of permanent magnets is formed as a magnet pole and is circumferentially placed between corresponding adjacent two of the plurality of projections
Implementation Method 2
a rotor, a dynamo-electric machine having the rotor and a rotor manufacturing method
Data Source
AI summary
A cover is configured into a tubular form and is fitted to a radially outer surface of each of projections of a rotor core and a radially outer surface of each of permanent magnets. A circumferential center portion of the radially outer surface of each projection contacts a radially inner surface of the cover. Circumferential end portions of the radially outer surface of each projection are radially inwardly spaced from the radially inner surface of the cover.