Brushless Motor Rotor Resin Segmentation for Size Reduction
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Solution Overview
Problem
The existing brushless motors face challenges in integrating a shaft, back yoke, and permanent magnet while maintaining mechanical strength and controlling the rotor size, as the resin portion on the inner circumferential surface of the back yoke requires a large mechanical strength to withstand centrifugal forces, leading to increased rotor size.
Innovation Solution
The brushless motor design incorporates a rotor with a shaft, back yoke, and permanent magnet, utilizing first and second resin portions to fix the back yoke and permanent magnet, and a communication hole with a third resin portion to connect them, reducing the mechanical strength required for the resin portion and minimizing rotor size, while a pressing member and magnet holder ensure proper positioning and support of the permanent magnet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the resin portion is formed on the entire inner circumferential surface of the back yoke to integrate the shaft, back yoke, and permanent magnet, then the integration is achieved, but the mechanical strength required for the resin portion increases and the rotor size increases
Solution Approach 1:
The resin portion is divided into multiple segments: first resin portions formed on both ends of the back yoke, and a second resin portion formed in a groove on the inner circumferential surface. This segmentation allows each resin portion to perform specific functions (fixing back yoke to shaft at ends, and providing bearing support in the groove) without requiring the entire resin structure to bear full centrifugal loads, thereby reducing the overall mechanical strength requirement and rotor size.
Solution Approach 2:
The bearing function is extracted from the resin portion formed on the entire inner circumferential surface and concentrated into a dedicated groove structure. This allows the resin to provide bearing support only where needed, rather than requiring continuous resin coverage for both integration and bearing functions, reducing the volume and mechanical strength requirements.
2Ease of operation
If the bearing is formed in the resin portion on the inner circumferential surface of the back yoke, then the shaft can be supported, but the resin portion needs relatively large mechanical strength to withstand centrifugal force
Solution Approach 1:
A groove structure is introduced as an intermediary element between the resin portion and the shaft. The groove provides a dedicated space for the resin to form a bearing, concentrating the shaft support function in a specific location. This allows the resin to provide effective bearing support with reduced mechanical strength requirements compared to forming the bearing in a continuous resin layer subjected to full centrifugal forces.
3Stability of the object's composition
If the resin portion is formed to fix the back yoke and permanent magnet, then the components are integrated, but the rotor size increases due to the required mechanical strength
Solution Approach 1:
The resin portions are segmented into discrete locations: first resin portions at both ends of the back yoke for fixing, and a second resin portion in the groove for bearing support. This segmentation achieves secure integration of the back yoke and permanent magnet while minimizing the volume of resin material required, thereby controlling rotor size.
Data Source
AI summary
A brushless motor may comprise a rotor comprising a shaft, a back yoke fixed on the shaft, a permanent magnet disposed at an outer circumference of the back yoke and first and second resin portions. The first resin portion may be formed at one ends of the back yoke and the permanent magnet and the second resin portion may be formed at other ends. The first and second resin portions may be fixed the back yoke and the permanent magnet. A communication hole communicating one end side and another end side in the shaft axis direction may be formed through the back yoke or between the shaft and the back yoke. A third resin portion connecting with the first and the second resin portions may be formed within the communication hole. The first, second and third resin portions may be formed integrally.