Permanent Magnet Rotor End Cap for Magnet Retention and Noise Damping
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Solution Overview
Problem
The existing assembly methods for radial flux electric motors with permanent magnet rotors are costly due to transportation of partially assembled rotor assemblies for overmolding and result in undesirable noise levels due to the hard plastic overmolding material not providing adequate noise attenuation.
Innovation Solution
A rotor assembly with a rotor core and end cap featuring deformable members that restrict magnet movement within radial apertures, manufactured from a softer plastic material to enhance noise attenuation and allow for single-site assembly, eliminating the need for transporting partially assembled rotors to an overmolding facility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overmolding is used to secure magnets within slots, then magnet retention is improved, but assembly cost increases due to transportation to different facility
Solution Approach 1:
The end cap integrates multiple functions: it secures magnets within slots using deformable members, provides noise attenuation, and eliminates the need for separate overmolding facility transportation. By combining magnet retention and noise attenuation functions into a single component manufactured at one facility, assembly cost is reduced while maintaining reliability.
Solution Approach 2:
The end cap serves multiple purposes simultaneously: it acts as a magnet retention mechanism through deformable members, provides noise attenuation through softer plastic material, and structurally supports the rotor assembly. This multi-functionality eliminates the need for separate overmolding operations at different facilities.
2Reliability
If hard plastic overmolding is used to secure magnets, then magnet retention is improved, but noise attenuation is worsened
Solution Approach 1:
The end cap uses softer plastic material with different physical properties compared to traditional hard plastic overmolding. This parameter change in material hardness provides effective noise attenuation while the deformable members within the end cap provide the necessary magnet retention functionality.
Solution Approach 2:
The end cap is constructed from softer plastic material that combines magnet retention capability through integrated deformable members with noise attenuation properties. This composite approach allows both functions to coexist in a single component without requiring hard plastic overmolding.
3Reliability
If deformable members are inserted into cavities, then magnet movement restriction is improved, but assembly complexity increases
Solution Approach 1:
The deformable members are pre-formed with specific geometries that enable them to deform upon insertion into cavities and automatically lock into position. This preliminary preparation of the deformable members simplifies the assembly process, as they require no additional fastening operations and self-secure upon insertion.
Solution Approach 2:
The deformable members utilize elastic deformation to transition from a compressed state during insertion to a locked state after insertion. This dynamic behavior allows the members to automatically secure magnets without requiring complex assembly tools or multiple operation steps.
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
The solution reduces assembly costs and effectively attenuates noise by restricting magnet movement and using a softer plastic material for noise damping, enabling complete rotor assembly at a single site without the need for additional transportation.
Implementation Method 1
The deformable members are configured to deform upon insertion into a cavity defined between the rotor core and the plurality of magnets
Implementation Method 2
The end cap is made from a softer plastic material than the overmolding material and, thus, noise generated by the rotor assembly is dampened by the end cap and does not propagate outward
Data Source
AI summary
A rotor assembly for use in a radial flux electric motor assembly is provided. The rotor assembly includes a rotor core having a plurality of circumferentially spaced rotor poles and a plurality of magnets alternately spaced with the plurality of rotor poles. The plurality of rotor poles define a radial aperture between each pair of circumferentially adjacent rotor poles, and each radial aperture is configured to receive a magnet of the plurality of magnets therein. The rotor assembly further includes an end cap coupled to the rotor core and to the plurality of core magnets. The end cap includes a plurality of deformable members positioned between the rotor core and the plurality of magnets and configured to restrict movement of the plurality of magnets within the radial apertures. The deformable members are configured to deform upon insertion into a cavity defined between the rotor core and the plurality of magnets.