Ferrite Magnet Rotor with Radial Polygonal Sections
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Solution Overview
Problem
The increasing cost and geopolitical issues related to rare-earth magnets make their use in motor vehicle electrical machines economically unsustainable, necessitating the use of ferrite magnets with lower residual magnetism, requiring larger volumes to achieve equivalent magnetic flows, which poses challenges in maximizing performance within dimensional and mechanical constraints.
Innovation Solution
A rotor design with permanent magnets featuring a radial section comprising a trapezoidal part near the central part and a rectangular part near the circumferential part, with a height ratio between 0.25 and 0.70, and a central tongue to maximize volume and mechanical strength, utilizing ferrite magnets to optimize performance while minimizing mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ferrite magnets with lower residual magnetism are used to replace rare-earth magnets, then cost is reduced, but the volume of magnets must be increased to achieve equivalent magnetic flow
Solution Approach 1:
The patent applies local quality by varying the magnet geometry in different radial zones. Magnets closer to the rotor center have a larger height-to-width ratio, while outer magnets have a smaller ratio. This optimized geometric distribution maximizes the magnetic flow contribution of each magnet volume element, enabling equivalent performance with reduced total magnet volume compared to uniform geometry designs.
Solution Approach 2:
The patent changes the geometric parameters of the magnets, specifically the height-to-width ratio, as a function of radial position. By optimizing this parameter distribution, the magnetic flow is maximized for a given total magnet volume, or equivalently, the required magnet volume is minimized for a target magnetic flow level, thus resolving the contradiction between magnet volume and rotor size.
2Quantity of substance
If the volume of ferrite magnets is increased to compensate for lower residual magnetism, then magnetic flow is maintained, but mechanical stresses on the rotor structure increase
Solution Approach 1:
The patent distributes the magnetic function non-uniformly across the rotor radius by optimizing the height-to-width ratio of magnets in different zones. This local optimization ensures that each magnet contributes maximally to the magnetic flow, reducing the total magnet volume required and consequently the mechanical stresses on the rotor structure, while maintaining the necessary magnetic performance.
Solution Approach 2:
The patent employs a composite structure consisting of magnets with optimized geometric ratios arranged in specific patterns, combined with a rotor core of appropriate magnetic permeability. This composite design achieves efficient magnetic flux distribution that reduces the burden on individual magnets and the overall mechanical stress on the rotor, while maintaining equivalent magnetic flow.
3Productivity
If the height-to-width ratio of magnets is optimized to maximize magnetic flow, then electrical performance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements local quality by assigning different height-to-width ratios to magnets in different radial zones. This geometric differentiation optimizes the magnetic flow contribution from each zone, improving overall electrical performance. The complexity is managed by implementing this gradient through modular magnet assemblies or standardized manufacturing processes that can produce different geometries efficiently.
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 design maximizes the volume of ferrite magnets, reducing the stator current intensity required for the same engine torque and effectively managing mechanical stresses, thereby enhancing the electrical performance and efficiency of the rotary electrical machine.
Implementation Method 1
synchronous machines with permanent magnets have extensive application in the field of motor vehicles
Implementation Method 2
rare-earth magnets of the neodymium—iron—boron (NeFeB), samarium—iron (SmFe), or samarium—cobalt (SmCo) type, which can have residual magnetism in excess of Tesla level
Data Source
AI summary
The rotor comprises of a plurality of alternating north poles (N) and south poles (S) formed from a plurality of permanent magnets (3) having a radial polygonal section and arranged in first recesses (4). These first recesses extend axially and are distributed regularly between a circumferential portion (5) and a central portion (6) of the magnetic mass (2) of the rotor in such a way as to define a plurality of circumferential polar sections (10). The radial section comprises a substantially rectangular portion (8) next to the circumferential portion adjacent to a substantially trapezoidal portion (7) next to the central portion. The rotor has a ratio (R) between a first height (h) of the trapezoidal portion and a second height (H) of the rectangular portion, in a radial direction, is predetermined in such a way as to maximize the efficiency of the electric machine.