Segmented Stator Sleeve for Lower Core Compression Stress
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Solution Overview
Problem
Electric motors face challenges with high compressive stresses during assembly, which can reduce flux-density capability and result in larger, heavier motors, especially when using cobalt iron alloys, and complicate disassembly and heat path issues.
Innovation Solution
A stator assembly with a sleeve that applies varying compressive stress to the stator core pack, using a design with distinct axial portions to manage stress and include features like anti-rotation grooves and tolerance rings for improved mechanical integrity and ease of assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If shrink-fitting is used to assemble the stator core pack into the motor housing, then mechanical integrity is improved, but compressive stresses increase and assembly complexity increases
Solution Approach 1:
The sleeve is divided into multiple axial portions (first portion, second portion, third portion) with different contact characteristics with the stator core pack. This segmentation allows different regions to serve different functions: providing mechanical support while reducing overall assembly complexity and compressive stresses.
Solution Approach 2:
Different portions of the sleeve have different local properties regarding contact with the stator core pack. The first and third portions are configured to contact the stator core pack to provide mechanical integrity, while the second portion is spaced from the stator core pack to reduce compressive stresses, creating local quality variations that resolve the contradiction.
2Strength
If shrink-fitting is used to assemble the stator core pack into the motor housing, then mechanical integrity is improved, but disassembly difficulty increases
Solution Approach 1:
The segmented sleeve design with spaced second portion creates a non-uniform stress distribution that allows for easier disassembly compared to uniform shrink-fitting, while maintaining mechanical integrity through the first and third portions that remain in contact with the stator core pack.
3Reliability
If cobalt iron alloys are used in the stator core pack, then flux density capability is improved, but sensitivity to compressive stress increases
Solution Approach 1:
The spaced second portion of the sleeve creates a local region with reduced compressive stress on the stator core pack, allowing cobalt iron alloys to be used effectively by protecting them from harmful compressive stresses in critical areas while maintaining flux density capability.
4Strength
If uniform compressive stress is applied to the stator core pack, then mechanical support is provided, but flux density capability decreases
Solution Approach 1:
The sleeve design creates non-uniform compressive stress distribution with the second portion spaced from the stator core pack to reduce stress in that region, while the first and third portions maintain contact to provide mechanical support. This local quality variation resolves the contradiction between mechanical support and flux density capability.
Solution Approach 2:
The segmented sleeve structure divides the compressive stress application into different axial regions, allowing the middle section to be stress-free or low-stress for optimal flux density, while end sections provide necessary mechanical support.
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 enhances flux-density capability, reduces motor size and weight, and simplifies assembly and disassembly while maintaining a low resistance heat path, allowing for the use of cobalt iron alloys under reduced stress.
Implementation Method 1
the sleeve is arranged to apply a compressive stress to the stator core pack
Implementation Method 2
the first portion of the sleeve is in contact with the stator core pack; the compressive stress applied by the first portion of the sleeve to the stator core pack is greater than the compressive stress applied by the second portion of the sleeve to the stator core pack
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A stator assembly (400) for an electric motor. The stator assembly includes a stator core pack (300) and a sleeve (200) for the stator core pack. The sleeve includes a first portion proximal to a first end of the sleeve and a second portion adjacent to the first portion of the sleeve. The stator core pack is at least partially within the sleeve and the first portion of the sleeve is in contact with the stator core pack. The sleeve is arranged to apply a compressive stress to the stator core pack and the stator assembly is arranged such that the compressive stress applied by the first portion of the sleeve to the stator core pack is greater than the compressive stress applied by the second portion of the sleeve to the stator core pack.