BLDC Motor Magnet Retention via Electromagnetic Forming
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Solution Overview
Problem
Existing methods for attaching permanent magnet segments to a rotor in brushless direct current (BLDC) motor assemblies are either unreliable, add weight and complexity, or increase manufacturing time and failure modes.
Innovation Solution
A method involving an annular ring made of electrically conductive material is used, which is shrunk using a high energy pulsed magnetic field to securely hold magnet segments in place on the rotor, eliminating the need for adhesives or additional fasteners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sleeve-like shell is used to secure magnet segments, then the magnet segments are retained, but the motor assembly gains undesirable weight, expense and complexity
Solution Approach 1:
The patent extracts the retention function from a separate mechanical component (sleeve-like shell) and integrates it into an electromagnetic field-based system. The conductive ring serves multiple functions: it conducts electricity for electromagnetic induction, provides structural support, and enables magnet segment retention through electromagnetic forces. This extraction eliminates the need for complex mechanical retention structures.
Solution Approach 2:
The conductive ring performs multiple functions simultaneously: it serves as an electrical conductor for electromagnetic induction, provides structural support for the magnet segments, and generates electromagnetic forces for retention. This multi-functionality replaces the need for separate retention components, reducing assembly complexity and weight.
2Reliability
If threaded fasteners are used to affix magnet segments, then the magnet segments are securely attached, but manufacturing assembly time increases and component complexities increase
Solution Approach 1:
The patent replaces the mechanical fastening system (threaded fasteners) with an electromagnetic system. The pulsed magnetic field induces eddy currents in the conductive ring, generating electromagnetic forces that compress and secure the magnet segments to the rotor hub. This substitution eliminates the need for time-consuming fastener installation while providing secure attachment.
Solution Approach 2:
The patent changes the retention mechanism from a static mechanical connection (threaded fasteners) to a dynamic electromagnetic force. By controlling the parameters of the pulsed magnetic field (frequency, amplitude, duration), the electromagnetic forces can be optimized for rapid magnet segment retention, significantly reducing assembly time compared to mechanical fastening.
3Reliability
If an annular ring is shrunk using high energy pulsed magnetic field, then magnet segments are held securely in tight pressing engagement, but high energy is required for the process
Solution Approach 1:
The patent uses periodic pulsed magnetic fields rather than continuous magnetic fields. The pulsed nature of the magnetic field allows for high energy density during the pulse duration to achieve the necessary electromagnetic forces for magnet segment retention, while the intervals between pulses allow for energy dissipation and reduce overall energy consumption. This periodic action enables effective retention with controlled energy input.
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 provides a reliable, lightweight, and cost-effective method for retaining magnet segments, reducing the risk of delamination and facilitating high-volume production while maintaining rotational balance and preventing obstruction in fluid pumping applications.
Implementation Method 1
rapidly shrinking the ring by inducing therein a powerful current flow using a high energy pulsed magnetic field
Data Source
AI summary
A BLDC electric motor assembly (24) includes a rotor (42) having a plurality of magnet segments (50) securely retained thereabout by an annular ring (68) which is shrunk in situ in an electromagnetic forming operation. The magnet segments (50) are formed with tongues (62, 64) on their upper and lower ends (56, 58). One tongue (64) seats in a retaining pocket (48) molded on the rotor shaft (40), whereas the other tongue (62) provides a ledge into which the ring (68) seats. After the magnet forming operation, wherein the ring (68) is shrunk, the outer surface of the ring (68) is flush with the outer surfaces (54) of the magnet segments (50).