Surface-Magnet Rotor Sleeve Locking With Indented Flange Collar
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Solution Overview
Problem
Existing electric motor rotors with surface magnets face issues of mechanical instability and increased assembly forces due to the deformation of protective covers during crimping, leading to potential cracks and reduced reliability, especially under high rotational speeds and temperatures.
Innovation Solution
A rotor design featuring a cylindrical rotor core with bread loaf-shaped surface magnets and a sleeve-like protective cover with a flange collar shaped into radially indented regions between the magnets, allowing for reduced assembly forces and enhanced mechanical stability by utilizing the non-circular shape of the rotor body for fastening, without material connection, using holding devices like glass fiber-reinforced injection-molded rings for magnet fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the protective cover is deformed by roller burnishing or pressing during crimping, then the protective cover is fastened to the rotor body, but the material of the protective cover is constricted leading to cracks and reduced mechanical stability
Solution Approach 1:
The patent divides the continuous protective cover into discrete fastening zones by shaping it to form protrusions that engage with recesses in the rotor body. This segmentation allows the protective cover to be fastened without constriction of the entire material, preventing cracks while maintaining mechanical stability.
Solution Approach 2:
The protective cover is given different local geometries: protrusions in regions requiring fastening and smooth continuous surfaces in other regions. This local differentiation enables targeted engagement with the rotor body without subjecting the entire protective cover to constriction forces during crimping.
2Stability of the object's composition
If the protective cover is deformed over the entire circumference during crimping, then the protective cover is fastened to the rotor body, but large assembly forces are required causing bulking and cambering
Solution Approach 1:
The fastening function is segmented to specific protrusion regions rather than applied continuously over the entire circumference. This allows the protective cover to be fastened effectively while requiring significantly reduced assembly forces, preventing bulking and cambering.
Solution Approach 2:
Instead of deforming the protective cover over the entire circumference (excessive action), the patent applies deformation only to specific protrusion regions (partial action). This partial action achieves sufficient fastening without the harmful effects of full-circumference crimping.
3Strength
If the outer circumference of the rotor body is made non-circular due to curvature of surface magnets, then the magnets are retained on the rotor core, but the protective cover cannot be uniformly positioned
Solution Approach 1:
The patent embraces the non-circular asymmetry created by the curved surface magnets and incorporates it into the protective cover design. The protective cover is shaped with corresponding protrusions that match the asymmetric rotor body geometry, enabling both magnet retention and proper protective cover positioning.
Solution Approach 2:
The protective cover is given different local geometries to match the asymmetric rotor body: protrusions in regions corresponding to magnet curvatures and smooth surfaces in other regions. This local adaptation allows the protective cover to be properly positioned while maintaining the benefits of the curved magnet design.
Data Source
AI summary
A rotor for an electric motor has a rotor body with a cylindrical rotor core and a number of surface magnets, which are distributed on a lateral surface of the rotor core in the form of rotor poles and which have a bread loaf-shaped cross-section with a convex curvature oriented towards the outer circumference. The rotor further has a sleeve-shaped protective cover, which is exposed on the outer circumference of the rotor body. The protective cover has a flange collar at least on an end face. The flange collar is shaped into radially indented regions between the curvatures of tangentially adjacent surface magnets resulting in a form-locking and/or a force locking connection between the radially indented regions and the surface magnets.