Rare-Earth Magnet Sintered Body for Cogging Torque Reduction
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Solution Overview
Problem
In magnet units with pillar-shaped magnets arranged in a circular cylindrical shape, an inter-edge gap forms between adjacent magnets, leading to a surface magnetic flux distribution that deviates from a sinusoidal wave shape, making it difficult to effectively reduce cogging torque.
Innovation Solution
The magnetization direction of pillar-shaped magnets is deviated by a given angle at circumferentially-opposite ends to achieve a sinusoidal wave-shaped surface magnetic flux distribution, using a rare-earth permanent magnet-forming sintered body with a specific three-dimensional structure and orientation of easy-to-magnetize axes, ensuring a sinusoidal wave-shaped magnetic flux distribution even at inter-end face gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pillar-shaped magnets are arranged in a circular cylindrical shape with inter-edge gaps, then the magnet structure is simple and easy to manufacture, but the surface magnetic flux distribution deviates from sinusoidal wave shape, making it difficult to reduce cogging torque
Solution Approach 1:
The patent applies different magnetization directions to different regions of the magnet. Specifically, the magnetization direction is set to vary continuously from the radial direction at the circumferential center to the tangential direction at the circumferential ends, creating local variations in magnetic properties that produce a sinusoidal flux distribution and reduce cogging torque while maintaining the simple pillar-shaped structure
Solution Approach 2:
The patent changes the magnetization direction parameter continuously across the magnet's circumference. By varying the magnetization angle from 0° (radial) at the center to 90° (tangential) at the ends, the patent transforms the magnetic flux distribution from non-sinusoidal to sinusoidal, effectively reducing cogging torque without altering the basic magnet geometry
2Object-affected harmful factors
If the magnetization direction is deviated at circumferential ends to achieve sinusoidal flux distribution, then cogging torque is reduced, but the orientation control becomes more complex
Solution Approach 1:
The patent incorporates the orientation variation directly into the magnet manufacturing process itself, rather than requiring post-manufacturing adjustment. The magnetization direction is controlled during the sintering or magnetization step, allowing the complex orientation pattern to be established in advance as part of the standard manufacturing process
Solution Approach 2:
The patent adds a circumferential dimension to the magnetization direction control. Instead of uniform magnetization in a single direction, the magnetization vector is varied in the circumferential direction, creating a two-dimensional magnetization pattern that achieves sinusoidal flux distribution and reduces cogging torque
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 reduces cogging torque in rotary electric machines by maintaining a sinusoidal wave-shaped magnetic flux distribution near inter-end face gaps, enhancing the magnetic efficiency and performance.
Implementation Method 1
the magnet material particles are oriented such that, their easy-to-magnetize axes are oriented, on a central radial line connecting the curvature center and a circumferential center point of the outer-side arc-shaped surface in a radially outward direction
Implementation Method 2
having a three-dimensional shape: a cross-section with a shape defined by a radially outer-side arc-shaped surface having a first curvature radius, a radially inner-side arc-shaped surface having a second curvature radius
Data Source
AI summary
This invention provides for a rare-earth permanent magnet-forming sintered body having an integral sintered structure of magnet material particles containing a rare-earth substance. The integral sintered structure is formed in a three-dimensional shape having: a cross-section with a shape defined by a radially outer-side arc-shaped surface having a first curvature radius, a radially inner-side arc-shaped surface having a second curvature radius less than the first curvature radius and having an arc shape concentric with the outer-side arc-shaped surface; and a first end face and a second end face each of which is a radially-extending face along a virtual radial line extending from a curvature center of the arc shapes; and an axial length extending in a direction perpendicular to the cross-section.