Electric Motor Rotor Magnet Locking via Overhanging Projections
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Solution Overview
Problem
Existing electric motor rotors with surface permanent magnets face challenges in securely fastening magnets to withstand centrifugal and magnetic forces without compromising output torque, as existing methods either fail to prevent magnet detachment or reduce magnetic flux density.
Innovation Solution
A rotor design featuring a cylindrically shaped core with magnets arranged at intervals, having overhanging parts locked by radially projecting locking projections, and filled with a binding agent to enhance stability and prevent magnetic flux short-circuits, while maintaining a suitable magnetic gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If holding projections are formed to lock permanent magnets, then magnet fastening reliability is improved, but holding projections may contact the stator causing magnetic flux short-circuit and reducing output torque
Solution Approach 1:
The locking projections are designed with a dual-dimensional structure: they extend in the radial direction to engage with magnets for secure fastening, while simultaneously having circumferential extent to lock magnets between adjoining projections. This two-dimensional locking mechanism prevents magnet displacement without requiring excessive radial projection that would cause stator contact.
Solution Approach 2:
The locking projections are strategically positioned and dimensioned to provide localized locking action at specific circumferential positions where magnets are attached, rather than requiring uniform radial extension across the entire rotor surface. This allows effective magnet retention while maintaining adequate magnetic gap in critical areas.
2Reliability
If distance between stator and rotor is increased to prevent contact, then magnet contact prevention is improved, but magnetic gap becomes larger reducing output torque
Solution Approach 1:
Instead of increasing radial distance to prevent magnet-stator contact, the invention uses circumferential locking projections that constrain magnets in the circumferential direction. This allows maintaining a smaller radial magnetic gap for higher output torque while preventing magnet contact through lateral confinement between adjoining projections.
3Power
If curvature rates of permanent magnets are reduced to realize larger torque, then output torque is improved, but magnets become more prone to detachment due to centrifugal force
Solution Approach 1:
The locking projections are pre-formed on the rotor core before magnet attachment, creating a mechanical interlocking structure that anticipates and counteracts the centrifugal forces that will act on magnets during operation. This preliminary mechanical constraint allows magnets to be retained securely even with reduced curvature rates that enable larger torque output.
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
The design effectively secures magnets to the rotor core, preventing detachment and maintaining high magnetic flux density, thus ensuring stable operation and output torque without interference with the stator.
Implementation Method 1
The permanent magnets of an SPM motor are acted on by the centrifugal force due to the rotational motion of the rotor
Implementation Method 2
the attraction force due to the magnetic force of the stator outward in the radial direction
Data Source
AI summary
In the rotor of the present invention, each magnet has an inward part adjoining the rotor core and an outward part positioned outward of the inward part in a radial direction of the rotor core. The outward has a facing surface which faces a stator and a pair of side surfaces which extend from two end parts of the facing surface in a circumferential direction toward the inward part. The inward part has a pair of overhanging parts which overhangs outward in the circumferential direction with respect to the pair of side surfaces of the outward part. Each locking projection of the rotor core passes between overhanging parts of two adjoining magnets and projects outward in the radial direction to engage with the overhanging parts.