Low-Friction Rotor Assembly for Press-Fit Sleeve Joining
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Solution Overview
Problem
Electric machine rotor assemblies face challenges in assembly due to high friction during press-fitting, which can lead to damage and increased costs, and existing methods lack efficient solutions to reduce friction while maintaining structural integrity under mechanical, electrical, and magnetic stresses.
Innovation Solution
A rotor assembly with a solid low-friction layer formed on its outer surface, made from materials like polybenzimidazole or tungsten disulfide, is press-fit into a carbon fiber sleeve, reducing friction and allowing higher press-stress without damage, and the method includes optional surface preparation and lubrication to facilitate assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rotor assembly is press-fitted into an outer sleeve, then structural support and robustness are improved, but high friction causes assembly damage and increased costs
Solution Approach 1:
A solid low-friction layer is introduced as an intermediary between the rotor assembly and the outer sleeve. This layer reduces friction during the press-fit operation, preventing damage to the rotor assembly while maintaining the structural support benefits of the press-fit connection. The layer acts as a mediator that enables the beneficial press-fit assembly without the harmful friction effects.
Solution Approach 2:
The friction coefficient at the interface between the rotor assembly and outer sleeve is changed by applying a solid low-friction layer. This parameter change reduces the friction force during press-fitting, allowing the assembly process to proceed without damage while maintaining the necessary structural integrity.
2Strength
If higher press-stress is applied during assembly, then structural robustness is improved, but friction-induced damage increases
Solution Approach 1:
The solid low-friction layer serves as a protective intermediary that enables higher press-stress to be applied during assembly. By reducing friction, it prevents the damage that would otherwise occur at high press-stress levels, allowing the rotor assembly to achieve the necessary robustness without compromising assembly integrity.
3Ease of operation
If a solid low-friction layer is applied, then friction and assembly forces are reduced, but manufacturing complexity increases
Solution Approach 1:
The friction coefficient is modified by applying a solid low-friction layer, which simplifies the assembly operation. While this adds a manufacturing step, the overall complexity is managed by using established coating and deposition techniques that integrate into existing manufacturing processes.
Solution Approach 2:
Certain solid low-friction materials utilize phase transitions during application or operation. For example, some materials transition from a softer application state to a harder operational state, or utilize thermal phase changes during the coating process, which can simplify the application method while maintaining the low-friction benefit.
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 approach reduces assembly forces, lowers fabrication costs, and enhances the robustness of the rotor assembly by minimizing stress and damage during press-fitting, while enabling higher press-stress application, making the process more cost-effective and manufacturing-friendly.
Implementation Method 1
A solid layer is formed on the outer surface of the rotor assembly and has an outer surface with a first coefficient of friction that is lower than a second coefficient of friction of the outer surface of the rotor assembly
Implementation Method 2
The rotor assembly is press-fit into the outer sleeve
Data Source
AI summary
A rotor for an electric machine includes a rotor assembly having an outer surface and including a plurality of poles with permanent magnets. A solid layer is formed on the outer surface of the rotor assembly and has an outer surface with a first coefficient of friction that is lower than a second coefficient of friction of the outer surface of the rotor assembly. The rotor includes an outer sleeve. The rotor assembly is press-fit into the outer sleeve.