Rotor Projections for Magnet Positioning and Cogging Torque Reduction
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Solution Overview
Problem
In SPM-type electric motors, cogging torque generated by magnetic interactions between permanent magnets and stator teeth complicates accurate control, necessitating precise magnet positioning to prevent unexpected torque generation.
Innovation Solution
A rotor design featuring projections on its outer surface with inclined sides and corresponding inclined magnet shapes, allowing for precise alignment by sliding the inclined sides of the magnets and projections, which face each other and define the same angle, facilitating accurate magnet placement and reducing cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets are mounted on the rotor surface, then the motor generates torque, but cogging torque is generated due to magnetic attraction and repulsion forces which complicates accurate control
Solution Approach 1:
The patent applies preliminary action by pre-positioning the permanent magnets on the rotor surface at specific locations and orientations before the motor operates. The magnets are arranged with their inclined sides facing each other in advance, creating a predetermined magnetic field distribution that reduces cogging torque from the outset, thereby enabling accurate control without requiring complex real-time adjustments.
2Manufacturing precision
If projections are added to restrict magnet movement, then magnet positioning is improved, but device complexity increases
Solution Approach 1:
The patent merges the positioning function into the rotor core structure itself by forming projections directly on the rotor surface. These projections serve dual purposes: they provide the mechanical structure needed to support the permanent magnets and simultaneously act as positioning elements that restrict magnet movement through their inclined sides. This integration eliminates the need for separate positioning mechanisms, reducing device complexity while maintaining high positioning precision.
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 enables easy and accurate positioning of permanent magnets, effectively preventing unexpected cogging torque and enhancing control over the electric motor.
Implementation Method 1
the first inclined side of the projection and the second inclined side of the permanent magnet which face each other incline, respectively, so as to define the same angle with respect to the direction of a rotational axis
Data Source
AI summary
A rotor includes a rotor core having an outer circumferential surface provided with projections extending in a direction of a rotational axis and projecting outwardly in a radial direction, and a plurality of permanent magnets arranged between the projections. The projections extend at an angle with respect to the direction of a rotational axis. The permanent magnets have inclined sides on both side faces, which incline with respect to the direction of a rotational axis. Side faces of the projections and the inclined side of the permanent magnets which face each other incline so as to define the same angle with respect to the direction of a rotational axis. An electric motor including such a rotor is also provided.