Rotor Permanent Magnet Gap Design for Centrifugal Stress Relief
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Solution Overview
Problem
In rotary electric machines, manufacturing errors in permanent magnets can lead to excessive stress and deformation of connection ribs due to centrifugal forces during high-speed rotation, as the circumferential center portion of the permanent magnet abuts the outer-circumference-lateral inner surface of the magnet insertion hole.
Innovation Solution
A rotor design featuring a gap between the circumferential center portion of the permanent magnet and the outer-circumference-side inner surface of the magnet insertion hole, with the permanent magnet supported by abutting on the inner surface at both ends, preventing direct contact and thus reducing stress on the connection ribs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the permanent magnet is fixed by surface contact with the rotor core, then the permanent magnet can be securely positioned, but excessive stress is generated in the circumferential center portion during high-speed rotation due to centrifugal force
Solution Approach 1:
A resin layer is introduced as an intermediary substance between the permanent magnet and the rotor core. This resin layer fills the gap between the magnet's outer circumferential surface and the magnet insertion hole, providing secure positioning while distributing centrifugal forces and preventing excessive stress concentration in the circumferential center portion.
Solution Approach 2:
The invention changes the physical state and distribution of the bonding interface by using a resin material that can flow and adapt to the gap geometry. The resin's viscoelastic properties allow it to accommodate manufacturing tolerances and distribute stresses uniformly, transforming the rigid contact interface into a compliant bonding layer.
2Manufacturing precision
If the permanent magnet is tightly fitted in the magnet insertion hole, then positioning precision is improved, but manufacturing errors cause excessive stress and deformation of connection ribs
Solution Approach 1:
The resin layer is applied beforehand to fill the gap between the permanent magnet and the magnet insertion hole, providing a cushioning effect that absorbs manufacturing errors and prevents excessive stress transmission to the connection ribs during operation.
Solution Approach 2:
The invention changes the mechanical properties of the interface by using a resin material with appropriate elasticity and bonding characteristics, transforming the rigid tight fit into a compliant bonded joint that accommodates dimensional variations without causing stress concentration.
3Stress or pressure
If a gap is provided between the permanent magnet and the magnet insertion hole, then stress during rotation is reduced, but positioning accuracy may deteriorate
Solution Approach 1:
The resin layer serves as an intermediary that fills the intentional gap between the permanent magnet and the magnet insertion hole, maintaining positioning accuracy through adhesion while allowing stress relief during high-speed rotation.
Solution Approach 2:
The resin forms a flexible bonding layer that maintains the permanent magnet's position through adhesion to both the magnet surface and the rotor core, while its flexibility allows it to accommodate centrifugal forces and reduce stress during rotation.
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 effectively prevents excessive stress and deformation of connection ribs by maintaining a gap between the permanent magnet's outer surface and the magnet insertion hole's inner surface, even with manufacturing errors, ensuring stable rotor operation.
Implementation Method 1
when the rotor rotates at a high speed, an excessive stress is generated due to the centrifugal force of the permanent magnet
Data Source
AI summary
A rotor for a rotary electric machine includes: a rotor core which includes a magnet insertion hole; and a permanent magnet housed in the magnet insertion hole. The permanent magnet has an arc shape which is convex toward an axial line. The rotor core includes: an outer-circumference core part; an inner-circumference core part; and connection ribs which connect the outer-circumference core part and the inner-circumference core part. The permanent magnet is supported in the rotor core in such a manner that circumferential ends abut on an inner surface of the magnet insertion hole. A circumferential center portion of the permanent magnet is separated from an outer-circumference-side inner surface of the magnet insertion hole. In the circumferential center portion of the permanent magnet, a gap is provided between an outer-circumference-side outer surface of the permanent magnet and the outer-circumference-side inner surface of the magnet insertion hole.