Non-Rectangular Rotor Magnets for Hybrid Motor Demagnetization
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Solution Overview
Problem
Existing hybrid electric vehicle systems face challenges in maintaining efficient motor performance due to demagnetization of permanent magnets, which reduces torque generation and overall efficiency, especially when the magnetic fields produced by the stator interact with the rotor.
Innovation Solution
The use of non-cuboid permanent magnets with a net magnetization direction parallel to the sideward surface, rather than perpendicular to any surface, reduces demagnetization risk, allowing for thinner magnets and simplified manufacturing, and are strategically arranged in inner and outer rows within magnet pockets on the rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cuboid permanent magnets with magnetization perpendicular to the outward surface are used, then the magnetic field strength is sufficient for torque generation, but the magnets are prone to demagnetization when exposed to stator magnetic fields
Solution Approach 1:
The patent applies asymmetry by changing the magnet geometry from a symmetric cuboid to an asymmetric non-cuboid parallelepiped form. The magnet has different dimensions in different directions (length L, width W, thickness T) with specific relationships (L>W>T) and non-perpendicular magnetization orientation. This asymmetric configuration optimizes the magnetic field distribution and reduces demagnetization risk by avoiding the perpendicular magnetization arrangement that creates high stress concentrations at the magnet poles.
Solution Approach 2:
The patent changes critical parameters including: (1) magnetization direction from perpendicular to outward surface to at an angle θ (45°<θ<90°) relative to the outward surface normal; (2) geometry parameters with specific relationships (L>W>T, L/W ratio, W/T ratio); (3) arrangement configuration from single row to multiple rows (inner and outer rows). These parameter changes collectively reduce demagnetization while maintaining torque generation capability.
2Reliability
If thicker permanent magnets are used to prevent demagnetization, then magnet durability improves, but the motor size and weight increase
Solution Approach 1:
The patent changes the magnetization direction parameter (angle θ relative to outward surface normal) and geometry parameters (L, W, T relationships) to optimize the magnetic field distribution. This allows achieving the required magnetic strength and durability with thinner magnets, thereby reducing rotor weight while maintaining reliability.
Solution Approach 2:
The patent transitions from a single-row magnet arrangement to a multi-row arrangement (inner and outer rows), effectively adding a dimensional aspect to the magnet configuration. This distributes the magnetic field generation across multiple rows, allowing each individual magnet to be thinner while collectively maintaining the required magnetic field strength and durability.
3Ease of manufacture
If non-cuboid parallelepiped magnets with angled magnetization are used, then demagnetization is reduced and manufacturing is simplified, but the magnetic field uniformity may be affected
Solution Approach 1:
The patent specifies precise parameter ranges and relationships (45°<θ<90°, L>W>T, specific L/W and W/T ratios) to optimize both manufacturability and magnetic field uniformity. These controlled parameter changes ensure that while the magnet geometry is simplified for manufacturing, the magnetic field distribution remains stable and uniform through careful geometric optimization.
Solution Approach 2:
The patent applies local quality by having different magnet dimensions and orientations optimized for their specific positions and functions. The non-cuboid parallelepiped shape with specific L, W, T relationships creates locally optimized magnetic field distribution that maintains overall uniformity while facilitating simplified manufacturing processes.
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 minimizes demagnetization, enabling the use of thinner magnets while maintaining performance, and simplifies the manufacturing process, thereby enhancing the efficiency and reliability of the motor in hybrid electric vehicles.
Implementation Method 1
an inverter configured to induce alternating currents in windings in a stator to establish magnetic fields that cause the rotor to rotate with respect to the stator
Implementation Method 2
a plurality of permanent magnets... Each magnet... has a net magnetization direction that is not perpendicular to any surface of the magnet
Data Source
AI summary
A hybrid powertrain utilizes a motor with a permanent magnet rotor. The rotor is formed by inserting parallelepiped magnets into slots. To reduce the likelihood of demagnetization, the net magnetization of each magnet is oriented parallel to a sidewards surface of the magnet and not perpendicular to an outwards surface of the magnet. The magnets may be arranged in multiple rows. The magnets in each row may be perpendicular to a rotor radial or diagonal to a rotor diagonal.