Embedded Magnet Rotor Core Holes for Faster Torque Response
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Solution Overview
Problem
Existing embedded magnet type rotary motors face challenges in improving torque responsiveness while maintaining torque levels, as described in Japanese Patent Application Laid-Open No. 2012-235608 does not adequately address this issue.
Innovation Solution
The embedded magnet type rotary motor incorporates a rotor core with permanent magnets spaced circumferentially and lightening holes that have inclined wall surfaces, positioned to minimize interference with magnetic poles and reduce moment of inertia, thereby enhancing torque responsiveness without reducing torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If lightening holes are formed in the rotor core to reduce weight and improve torque responsiveness, then the moment of inertia is reduced and torque responsiveness is improved, but the torque may be reduced due to loss of magnetic material
Solution Approach 1:
The patent applies local quality by creating lightening holes with specific geometric features (inclined outer circumferential wall surfaces) in localized regions of the rotor core. This allows the rotor core to have different properties in different locations: the lightening holes reduce weight and moment of inertia in non-critical areas, while the inclined surfaces preserve magnetic flux paths in critical areas near the permanent magnets, thus maintaining torque while improving responsiveness.
2Weight of moving object
If the rotor core weight is reduced to improve responsiveness, then the moment of inertia decreases and torque change response improves, but the structural strength and torque generation capability may be compromised
Solution Approach 1:
The lightening holes are designed with inclined outer circumferential wall surfaces that strategically preserve structural integrity in critical load-bearing regions while removing material in less critical areas. This localized approach reduces overall weight and moment of inertia while maintaining sufficient structural strength for reliable operation.
Solution Approach 2:
The rotor core employs a composite structure combining magnetic material with strategic voids (lightening holes). This composite design optimizes the balance between weight reduction and magnetic performance, creating a structure that is both lightweight and mechanically sound.
3Reliability
If thin plate-shaped high-permeability members are stacked at the outer peripheral part of the rotor core to suppress eddy currents, then eddy current loss is reduced and structural reliability is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses lightening holes (porous structure) in the rotor core to reduce eddy current paths and losses. This porous design achieves the goal of suppressing eddy currents and improving reliability while avoiding the complexity of stacking thin high-permeability plates, as the hollow cylindrical structure with strategic voids provides similar eddy current suppression benefits.
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
The motor achieves improved torque responsiveness while maintaining torque levels, leading to more efficient energy use and reduced carbon emissions in electric devices.
Implementation Method 1
a stator that has a stator coil; and a rotor having a rotor core with a plurality of permanent magnets embedded therein and held inside the stator so as to be rotatable about a rotation axis
Implementation Method 2
the rotor core has a plurality of lightening holes spaced from each other in the circumferential direction on the rotation axis side of the plurality of permanent magnets
Data Source
AI summary
A rotary motor comprises a stator; and a rotor having a core with a plurality of permanent magnets embedded therein and held inside the stator for rotation around a rotation axis, wherein the magnets are in the outer circumference of the core, spaced apart in a circumferential direction, and have magnetic poles at both ends in the circumferential direction. The core has a plurality of lightening holes in the circumferential direction on the rotation axis side of the permanent magnets; each hole having a bottom wall surface extending in the circumferential direction on the rotation axis side, an outer circumferential wall surface on the outer circumferential side, and a side wall surface between the bottom wall surface and the outer wall surface; and the outer wall surface has an inclined portion that approaches the rotation axis as it moves from the center of the permanent magnets toward the magnetic pole.