Segmented Rotor Design for Permanent Magnet Motor Stress Management
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Solution Overview
Problem
Permanent magnet motors experience performance deterioration, noise, and vibration due to stress-induced expansion when a rotary shaft with a larger diameter is inserted into the rotor, leading to potential cracking or chipping of magnets and uneven gaps between the rotor and stator.
Innovation Solution
The rotor design incorporates magnet insert holes with gaps between permanent magnets and semi-tubular rivet insert holes with gaps between semi-tubular rivets, along with passage holes and interlocks, to absorb stress and maintain even gaps, reducing expansion and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rotary shaft with a larger diameter is inserted into the rotor by shrink fitting or press fitting, then the rotor achieves structural integrity and rotational support, but the inner wall surface of the rotary shaft insert hole is pressed causing the outside diameter of the rotor to expand
Solution Approach 1:
The rotor is divided into multiple independent magnetic pole pieces (main magnetic poles and auxiliary magnetic poles) that are assembled together. This segmentation allows each pole piece to independently accommodate the expansion stress from rotary shaft insertion without transmitting it to the entire rotor structure, thereby maintaining outside diameter precision while achieving structural integrity through the combined assembly.
Solution Approach 2:
Different regions of the rotor are designed with different properties: main magnetic poles contain magnet insert holes with precise positioning for permanent magnets, while auxiliary magnetic poles provide structural support and accommodate expansion. This local differentiation allows specific areas to handle expansion stress without affecting the overall outside diameter precision.
2Reliability
If the outside diameter of the rotor expands due to rotary shaft insertion, then the rotary shaft achieves secure fixation, but harmonic components of the induced electromotive force increase causing iron loss and performance deterioration
Solution Approach 1:
By segmenting the rotor into multiple magnetic pole pieces with alternating main and auxiliary poles, the design isolates expansion stress to local regions. This prevents uniform expansion that would otherwise increase harmonic components and iron loss, while still achieving secure rotary shaft fixation through the integrated assembly of all pole pieces.
3Ease of operation
If the outside diameter of the rotor expands unevenly, then the rotary shaft achieves insertion, but the gap between the outer circumferential surface of the rotor and the inner circumferential surface of the stator becomes unevenly narrowed causing noise and vibration
Solution Approach 1:
The rotor is segmented into alternating main and auxiliary magnetic poles, where auxiliary poles specifically accommodate expansion stress from rotary shaft insertion. This segmentation ensures that expansion occurs in controlled regions without causing uneven narrowing of the air gap, thereby preventing noise and vibration while maintaining insertion feasibility.
Solution Approach 2:
The rotor design employs asymmetric distribution of magnetic pole types (main and auxiliary) around the circumference. This asymmetric arrangement allows strategic placement of expansion-accommodating auxiliary poles at specific locations, enabling controlled expansion that maintains uniform air gap dimensions and prevents noise and vibration.
4Strength
If stress acts upon the rotor to expand its outside diameter, then the rotary shaft achieves secure mounting, but the permanent magnets may be cracked or chipped
Solution Approach 1:
The rotor is divided into separate magnetic pole pieces, with permanent magnets installed only in main magnetic poles. Auxiliary magnetic poles serve as stress-absorbing structural elements that accommodate expansion from rotary shaft insertion. This segmentation isolates permanent magnets from expansion stress, ensuring magnet integrity while achieving secure mounting.
Solution Approach 2:
Auxiliary magnetic poles act as intermediary elements between the rotary shaft and main magnetic poles containing permanent magnets. These auxiliary poles absorb and distribute expansion stress, preventing direct transmission of stress to permanent magnets, thereby protecting them from cracking or chipping while still enabling secure rotary shaft mounting.
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 reduces stress-induced expansion, prevents magnet damage, and minimizes noise and vibration, enhancing motor performance and reliability.
Implementation Method 1
a rotor having magnet insert holes for receiving permanent magnets
Implementation Method 2
The shrink fitting is effected by enlarging the bore diameter of the rotary shaft insert hole 859 by heating the rotor 850
Implementation Method 3
The press fitting is effected by inserting the rotary shaft 860 into the rotary shaft insert hole 859 by pushing in the rotary shaft 860 with a strong force
Data Source
AI summary
A rotary shaft 60 having an outside diameter larger than the bore diameter of a rotary shaft insert hole 59 of a rotor 50 is inserted into the rotary shaft insert hole 59. A magnet insert hole 51a1 is provided in a main magnetic pole [a] of the rotor 50. Permanent magnets 52a1 to 52a3 are inserted into the magnet insert hole 51a1 such that a gap is formed between the permanent magnets 52a1 to 52a3 and the magnet insert hole 51a1. A semi-tubular rivet insert hole 55a and interlocks 57a1, 57a2 elongated in the radial direction of the rotor are disposed radially outward of the magnet insert hole 51a in the rotor. A semi-tubular rivet 56a is inserted into the semi-tubular rivet insert hole 55a such that a gap is formed between the semi-tubular rivet 56a and the semi-tubular rivet insert hole 55a. Passage holes 58ab, 58da are provided in the auxiliary magnetic poles [ab], [da].