Rotor Magnet Powder Coating for Self-Centering Adhesion
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Solution Overview
Problem
Existing methods for fixing permanent magnets to rotors in electrical machines face challenges due to premature reaction of the prepolymer coating, leading to reduced structural stability and inaccurate positioning of the magnets.
Innovation Solution
A process involving a dry powder coating with a prepolymer, hardener, functional filler, and a chemical blowing agent is used. The chemical blowing agent reacts upon activation, expanding the coating matrix to securely adhere the magnet to the rotor pocket without premature reaction, ensuring stability and accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermally expandable microspheres are used as blowing agent, then self-centering of permanent magnets in rotor pockets is achieved, but premature reaction of prepolymer with microspheres occurs
Solution Approach 1:
The patent changes the chemical parameters of the blowing agent from thermally expandable microspheres to chemical blowing agents (such as azodicarbonamide, ammonium bicarbonate, or sodium bicarbonate). These chemical blowing agents decompose at specific temperatures to release gas, achieving the same expansion effect without causing premature reaction with the prepolymer, thus resolving the contradiction between positioning accuracy and structural stability.
Solution Approach 2:
The patent employs chemical blowing agents that are consumed during the expansion process (decompose to release gas), replacing the reusable but problematic thermally expandable microspheres. This disposable approach eliminates the harmful interaction while maintaining the beneficial self-centering effect.
2Ease of manufacture
If large manufacturing tolerances are accepted for economic production, then production cost is reduced, but accurate positioning of permanent magnets becomes difficult
Solution Approach 1:
The patent implements a self-centering mechanism where the chemical blowing agent expands the coating material during curing, automatically positioning the permanent magnets centrally in the rotor pockets. This self-adjusting process eliminates the need for tight manufacturing tolerances and precise manual positioning, allowing economic production with larger tolerances while maintaining high positioning accuracy.
Solution Approach 2:
The patent utilizes the phase transition of chemical blowing agents from solid to gas during heating, which causes the coating material to expand and flow into gaps, automatically centering the permanent magnets. This phase change-driven self-adjustment compensates for manufacturing tolerances without requiring precise initial positioning.
3Productivity
If premixed coating material is prepared in advance, then production efficiency is improved, but structural stability of coated magnets deteriorates during transport and storage
Solution Approach 1:
The patent prepares the coating material with chemical blowing agents in advance (premixed), enabling efficient production. The chemical blowing agents remain stable during storage and only decompose during the curing process, providing both production efficiency and structural stability during transport and storage, unlike thermally expandable microspheres that caused premature reactions.
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 solution allows for accurate and stable adhesion of permanent magnets to rotor pockets, even with large manufacturing tolerances, maintaining structural integrity during transport, storage, and high-temperature operation.
Implementation Method 1
the blowing agent is a chemical blowing agent
Data Source
AI summary
The invention relates to a process for coating a magnet to be inserted into a pocket of a rotor comprising the steps of providing a permanent magnet, and applying a dry powder coating comprising a prepolymer, a hardener, at least one functional filler and a blowing agent. In order to avoid premature reaction of the prepolymer, the blowing agent is a chemical blowing agent. Further, the invention relates to a permanent magnet to which a process according to the invention was applied and to a rotor comprising a permanent magnet to which a process according to the invention was applied.