Injection-Molded Rotor Stack Filling to Prevent Deformation
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Solution Overview
Problem
Conventional reluctance motor rotors with stacked laminations and manually inserted magnets are costly and complex due to tight tolerances, complex magnet shapes, and manual alignment challenges.
Innovation Solution
A method of molding magnetic material directly into rotor cavities using a polymer melt with controlled injection and packing pressures to form reluctance rotors, eliminating the need for pre-fabricated magnets and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual magnet insertion is used in conventional rotor production, then magnet alignment and insertion can be performed, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent combines the magnet insertion process with the rotor lamination stacking process by providing a pre-assembled rotor-lamination-magnet unit to the injection molding machine. This merging eliminates the need for separate manual magnet alignment and insertion steps, directly reducing manufacturing complexity while maintaining ease of manufacture.
Solution Approach 2:
The patent performs preliminary assembly of magnets onto rotor laminations before the injection molding process. By pre-attaching magnets to laminations and pre-assembling the rotor stack, the complex magnet insertion operation is converted into a simple placement operation, reducing the complexity of the main manufacturing process.
2Manufacturing precision
If tight tolerances are maintained for magnet and lamination alignment, then rotor precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent performs preliminary positioning of magnets relative to laminations before final rotor assembly. By pre-attaching magnets to laminations with proper alignment and pre-assembling the rotor stack, the tolerances are established early in the process, allowing for cost-effective manufacturing without requiring expensive tight tolerance control during final assembly.
Solution Approach 2:
The patent enables the rotor-lamination-magnet unit to self-align and self-position during the injection molding process. The pre-assembled unit maintains its internal tolerances without requiring external alignment operations, achieving manufacturing precision while reducing production cost by eliminating complex alignment procedures.
3Reliability
If complex magnet shapes are fabricated, then rotor performance is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent introduces polymer material as an intermediary that bonds magnets to laminations. This intermediary not only secures the magnets but also allows for cost-effective fabrication of complex magnet shapes, as the polymer can be molded into any required geometry to match the stator pole pieces, achieving improved rotor performance without proportionally increasing manufacturing cost.
Solution Approach 2:
The patent uses composite materials consisting of polymer and magnetic particles to create the bonding material. This composite material can be molded into complex shapes that match the required magnet geometries, enabling improved rotor performance while maintaining cost-effective manufacturing through injection molding processes.
4Manufacturing precision
If rotor deformation is prevented during injection molding, then rotor quality is improved, but cycle time may increase
Solution Approach 1:
The patent performs preliminary preparation of the rotor-lamination-magnet unit before injection molding, including pre-heating and pre-positioning. By preparing the rotor stack in advance with proper temperature and positioning, the actual injection molding process can proceed quickly without requiring extended holding times for deformation prevention, thus improving rotor quality while maintaining productivity.
Solution Approach 2:
The patent optimizes injection molding parameters such as temperature, pressure, and injection rate to prevent rotor deformation. By carefully controlling these parameters within optimal ranges, the process achieves high rotor quality with minimized cycle time, as the optimized parameters allow for faster injection and cooling without causing thermal or mechanical deformation.
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 method reduces production costs and complexity while ensuring adequate tolerances and preventing rotor deformation, optimizing cycle time and fill mass, resulting in high-quality reluctance rotors.
Implementation Method 1
filling a first volume of the polymer melt into the cavities of the rotor at a first pressure and filling a second volume of the polymer melt into the rotor at one or more second pressures
Data Source
AI summary
A method for molding a magnetic material into a rotor stack, including providing a polymer melt including magnetic compound particles and a polymer binder, providing a rotor including a plurality of cavities, the rotor being arranged in a mold having a mold cavity surface, and providing a gap between the outer periphery of the rotor and the mold cavity surface. The method also includes filling a first volume of the polymer melt into the cavities of the rotor at a first pressure and filling a second volume of the polymer melt into the rotor at one or more second pressures, the one or more second pressures being less than the first pressure and above an ambient pressure.