Injection Molded Magnet Shapes for Torque Ripple Reduction
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Solution Overview
Problem
Torque ripple in electric machines, which causes noise and iron losses, is a significant design challenge that existing technologies have not adequately addressed without increasing manufacturing complexity and cost.
Innovation Solution
The internal permanent magnet machine employs a rotor core with cavities of different shapes, where magnets are injection molded to match these cavities, allowing for a pre-defined configuration that minimizes torque ripple by varying the shape and size of pole cavities, thereby reducing the need for pre-formed magnets and simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If traditional uniform pole cavities are used in rotor assembly, then manufacturing process is simple, but torque ripple is high causing noise and iron losses
Solution Approach 1:
The patent applies local quality by varying the shape and dimensions of pole cavities at different locations around the rotor periphery. Each pole cavity is designed with specific local characteristics (different widths, lengths, or cross-sectional shapes) tailored to its position, creating non-uniform magnetic field distribution that compensates for torque ripple. This localized customization of cavity geometry allows torque optimization without requiring complete redesign of the entire rotor structure.
Solution Approach 2:
The patent implements asymmetry by deliberately designing pole cavities with asymmetric or varied geometries rather than uniform symmetric shapes. The cavities may have different cross-sectional areas, varying depths, or asymmetric positioning relative to the rotor centerline. This asymmetric configuration creates intentional imbalances in magnetic flux distribution that counteract the periodic torque variations, reducing torque ripple while maintaining manufacturing feasibility through standardized molding processes.
2Object-generated harmful factors
If pre-formed magnets are used to reduce torque ripple, then torque ripple reduction is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring the pole cavities with optimized asymmetric geometries during the rotor core manufacturing stage, before magnet installation. The cavity shapes are designed in advance to create the desired magnetic field distribution patterns. This preliminary structuring of the magnetic circuit allows standard magnets to produce the torque ripple reduction effect without requiring custom-shaped magnets, thereby simplifying the overall manufacturing process while achieving the torque optimization goal.
Solution Approach 2:
The patent uses copying by creating multiple identical pole cavities with the same optimized asymmetric geometry that is replicated around the rotor periphery. Instead of designing unique complex magnet shapes for each pole position, the same cavity template is copied and positioned at different locations, each tailored to local requirements. This copying approach standardizes the manufacturing process while achieving location-specific torque ripple compensation, reducing both manufacturing complexity and cost.
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 effectively reduces torque ripple in electric machines without significantly increasing manufacturing complexity or cost, by forming magnets within the rotor core cavities to match their specific shapes, thereby optimizing magnetic interaction and reducing noise and iron losses.
Implementation Method 1
Each of the plurality of magnets is injection molded into their respective cavity of the plurality of first pole cavities and the plurality of second pole cavities
Implementation Method 2
The molten magnetic material within each of the plurality of first pole cavities and the plurality of second pole cavities of the rotor core is then cooled to form a plurality of magnets
Implementation Method 3
The rotor core magnetically interacts with the wound stator for rotation about a central axis of rotation
Data Source
AI summary
An internal permanent magnet machine includes a wound stator, and a rotor core. The rotor core includes a plurality of first pole cavities, and a plurality of second pole cavities. One of a plurality of magnets is disposed within each of the pole cavities, and is injection molded into their respective cavity. The first pole cavities and the second pole cavities are each arranged in a pre-defined configuration, such that each pole cavity of the first pole cavities is identically positioned with one of the pole cavities of the second pole cavities within their respective pre-defined configurations, to define a corresponding pair of pole cavities. The pole cavity of the first pole cavities and the pole cavity of the second pole cavities of at least one of the corresponding pair of pole cavities define a different shape relative to each other.