Rotor Core Projections for Magnet Positioning
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Solution Overview
Problem
Conventional SPM motors with magnets attached to the outer circumferential surface of a rotor core require extensive machining for guide projections, increasing manufacturing costs and risking magnet detachment due to insufficient bonding strength under centrifugal forces.
Innovation Solution
A rotor design featuring a cylindrical rotor core with projections only on part of its height, allowing for reduced machining hours and improved magnet positioning, using a combination of projection-equipped and projection-less cylindrical parts with magnets bonded to the latter's curved surface to prevent binder removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If guide grooves are formed on the entire length of the rotor core to position magnets, then magnet positioning accuracy is improved, but machining man-hour and manufacturing costs increase
Solution Approach 1:
The rotor core is divided into two distinct parts: a first rotor core part with guide grooves formed on its outer circumferential surface, and a second rotor core part without guide grooves. This segmentation allows guide grooves to be formed only where necessary for magnet positioning, reducing overall machining requirements while maintaining positioning accuracy at critical locations.
Solution Approach 2:
Guide grooves are provided only on the first rotor core part rather than uniformly across the entire rotor core. This local quality approach concentrates machining efforts only in regions where magnet positioning is critical, eliminating unnecessary machining on the second rotor core part and thereby reducing total machining man-hour while preserving essential positioning functionality.
2Manufacturing precision
If guide grooves are formed on the entire length of the rotor core, then magnet positioning is improved, but manufacturing costs increase
Solution Approach 1:
The rotor core is divided into two distinct parts: a first rotor core part with guide grooves formed on its outer circumferential surface, and a second rotor core part without guide grooves. This segmentation allows guide grooves to be formed only where necessary for magnet positioning, reducing overall machining requirements while maintaining positioning accuracy at critical locations.
Solution Approach 2:
Guide grooves are provided only on the first rotor core part rather than uniformly across the entire rotor core. This local quality approach concentrates machining efforts only in regions where magnet positioning is critical, eliminating unnecessary machining on the second rotor core part and thereby reducing total machining man-hour while preserving essential positioning functionality.
3Reliability
If magnets are attached to the rotor core after magnetization, then magnetic properties are preserved, but binder is removed from between magnet surfaces and groove surfaces due to attraction force
Solution Approach 1:
The guide grooves are pre-formed on the rotor core surface before magnet attachment. These grooves create intentional gaps between the magnet confronting surfaces and the rotor core outer circumferential surface. When magnets are attached after magnetization, the pre-existing groove structure prevents direct surface-to-surface contact, eliminating the binder removal issue caused by magnetic attraction while preserving magnetic properties.
4Ease of manufacture
If magnets are attached with flat confronting faces to guide grooves, then manufacturing cost is reduced, but bonding strength decreases due to binder removal under centrifugal force
Solution Approach 1:
The guide grooves are pre-formed on the rotor core surface before magnet attachment. These grooves create intentional gaps between the magnet confronting surfaces and the rotor core outer circumferential surface. When magnets are attached after magnetization, the pre-existing groove structure prevents direct surface-to-surface contact, eliminating the binder removal issue caused by magnetic attraction while preserving magnetic properties.
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 machining time and costs while enhancing bonding strength, preventing magnet scattering and maintaining structural integrity during rotation.
Implementation Method 1
the outer circumferential surface of the rotor core is formed with a plurality of projections for positioning the plurality of magnets in the circumferential direction of the rotor core
Implementation Method 2
segment type permanent magnets fixed by a thermosetting binder to the outer circumferential surface of a rotor core
Implementation Method 3
the flat confronting faces CS of the magnets M will closely contact the flat bottom surfaces BS of the guide grooves G due to the attraction force
Implementation Method 4
the bonding strength acting on the magnets will fall, and therefore the centrifugal force which accompanies rotating motion of the rotor R is liable to cause the magnets M to be scattered from the rotor core C
Data Source
AI summary
A rotor of the present invention comprises a cylindrically shaped rotor core, and a plurality of magnets arranged at predetermined intervals at an outer circumferential surface of the rotor core. The outer circumferential surface of the rotor core is formed with a plurality of projections for positioning the plurality of magnets in the circumferential direction, and each of the projections extends over only part of outer circumferential surface of the rotor core in the height direction. The rotor core includes a projection-equipped cylindrical part which has an outer circumferential surface over which the plurality of projections extend, and a projection-less cylindrical part which has an outer circumferential surface over which the plurality of projections do not extend.