Permanent Magnet Rotor Structure for Stable Motor Torque
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Solution Overview
Problem
Existing electric motors with rotor cores and permanent magnets face challenges in maintaining the position and stability of permanent magnets due to magnetic resistance and centrifugal forces, leading to potential damage from collisions within the rotor core.
Innovation Solution
The design incorporates a rotor core with through holes and sintered permanent magnets, where the length of the rotor core in the radial direction is shorter than the permanent magnet, creating a magnetic circuit with varying magnetic resistance to securely hold the magnets in place using both magnetic and centrifugal forces, and includes specific configurations of through holes and rib structures to enhance torque and demagnetization resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the rotor core length in radial direction is increased to hold permanent magnets, then magnet position stability improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The rotor core is segmented into multiple through-holes arranged in the circumferential direction, each holding a permanent magnet. This segmentation allows the magnets to be securely positioned without requiring a solid, complex rotor core structure, thus maintaining stability while reducing overall device complexity.
Solution Approach 2:
The rotor core length in the radial direction is made shorter than the permanent magnet length, creating a local quality difference. This allows the permanent magnets to extend beyond the rotor core radially, providing secure positioning through the magnetic circuit while avoiding the need for a uniformly long rotor core that would increase complexity.
2Power
If the rotor core length in radial direction is made shorter than permanent magnet length, then torque and demagnetization resistance increase, but magnetic resistance management becomes more challenging
Solution Approach 1:
The rotor core length is made shorter than the permanent magnet length in the radial direction, creating a specific local geometry. This configuration increases torque and demagnetization resistance by optimizing the magnetic flux path, while the magnetic resistance is managed through the specific arrangement of through-holes and rib structures.
Solution Approach 2:
Multiple through-holes are arranged in the circumferential direction, segmenting the magnetic circuit into distinct paths. This segmentation allows for optimized magnetic flux flow through each hole while managing overall magnetic resistance, achieving high torque without excessive complexity.
3Ease of manufacture
If permanent magnets are held by resin injection in gap between rotor core and magnet, then magnet positioning is achieved, but manufacturing precision and reliability are compromised
Solution Approach 1:
The permanent magnets are extracted from the traditional embedding method and positioned in through-holes that extend through the rotor core. This extraction allows for more reliable positioning while maintaining ease of manufacture through simplified assembly processes.
Solution Approach 2:
The rotor core is divided into multiple through-holes, segmenting the magnet positioning into discrete, manageable locations. This segmentation enables precise magnet placement and secure holding without requiring complex resin injection processes, improving both reliability and manufacturability.
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 configuration effectively positions and secures the permanent magnets, reducing magnetic resistance, increasing torque and demagnetization resistance, and protecting the magnets from damage, while allowing efficient magnetic flux flow and cooling through a refrigerant flow path.
Implementation Method 1
The permanent magnets generate a magnetic flux in a magnetic circuit
Implementation Method 2
The magnetic circuit shows a smaller magnetic resistance in a portion of the rotor radially outward of the permanent magnets than in a portion of the rotor radially inward of the permanent magnets
Implementation Method 3
securely hold the magnets in place using both magnetic and centrifugal forces
Data Source
AI summary
An electric motor includes a stator, and a rotor having a plurality of magnetic poles. Each magnetic pole includes a rotor core having through holes arranged circumferentially side by side, and a permanent magnet inserted into each through hole. A length of a portion of the rotor core in a radial direction of the rotor is shorter than a length of the permanent magnet in the radial direction of the rotor. The length of the portion of the rotor core is measured between an inner surface of each of the through holes adjacent to an outer periphery of the rotor and an outer peripheral surface of the rotor. The permanent magnets generate a magnetic flux in a magnetic circuit showing a smaller magnetic resistance in a portion of the rotor radially outward of the permanent magnets than in a portion of the rotor radially inward of the permanent magnets.