Halbach Rotor Magnet Layout for Inner-Side Sensor Detection
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Solution Overview
Problem
In motors with a Halbach array permanent magnet, the reduced magnetic field intensity on the radially inner side makes it difficult for magnetic sensors to detect the magnetic field accurately, leading to deteriorated detection accuracy.
Innovation Solution
A rotor magnet with a Halbach array configuration that includes radially and non-radially magnetized portions, along with a non-magnetized void portion between the radially magnetized portions, is positioned to enhance magnetic field detection on the radially inner side by allowing magnetic flux to flow inward, improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a Halbach array permanent magnet is used to increase magnetic field intensity on the radially outer side, then motor output is improved, but magnetic field intensity on the radially inner side decreases
Solution Approach 1:
The rotor magnet is divided into multiple magnetized portions with different magnetization directions. Specifically, first magnetized portions are magnetized in the radial direction, second magnetized portions are magnetized in the axial direction, and third magnetized portions are magnetized in the circumferential direction. This local differentiation of magnetization directions allows the magnetic field intensity to be enhanced on the radially outer side for improved motor output while simultaneously maintaining adequate magnetic field intensity on the radially inner side for sensor detection.
2Object-affected harmful factors
If magnetic sensor is arranged on the radially inner side of the permanent magnet, then interference with stator magnetic field is avoided, but detection accuracy deteriorates due to decreased magnetic field intensity
Solution Approach 1:
The rotor magnet incorporates third magnetized portions that are magnetized in the circumferential direction, specifically positioned to enhance magnetic field intensity in regions where the magnetic sensor is located on the radially inner side. This local enhancement of magnetic field intensity in the circumferential direction allows the magnetic sensor to detect sufficient magnetic field signals while remaining on the radially inner side, thus avoiding interference with the stator magnetic field.
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 configuration effectively increases the magnetic flux density detected by the sensor on the radially inner side, enhancing the accuracy of rotational position detection while maintaining motor output.
Implementation Method 1
The rotor magnet has a plurality of magnetized portions arranged along a circumferential direction in a Halbach array to increase a magnetic field intensity on the one side in the radial direction
Implementation Method 2
A non-magnetized portion is provided in an axial portion of the rotor magnet where a magnetic field is detected by the magnetic sensor. The non-magnetized portion is located between the first radially magnetized portion and the second radially magnetized portion in the circumferential direction
Implementation Method 3
a magnetic sensor capable of detecting a magnetic field of the rotor magnet
Data Source
AI summary
A motor includes a rotor magnet, a stator, and a magnetic sensor. The rotor magnet includes magnetized portions in a Halbach array, and having radially magnetized portions whose magnetization direction is a radial direction and non-radially magnetized portions. In first and second radially magnetized portions, magnetic poles on both sides in the radial direction are arranged opposite to magnetic poles on both sides in the radial direction of the first radially magnetized portion. The first and second radially magnetized portions are alternately arranged along a circumferential direction with at least one non-radially magnetized portion therebetween. The magnetic sensor is located on the other side in the radial direction with respect to the rotor magnet. A non-magnetized portion is in an axial portion of the rotor magnet where a magnetic field is detected by the magnetic sensor, and located between the first and second radially magnetized portions in the circumferential direction.