Permanent Magnet Rotor Slit Layout for Low Vibration Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing permanent magnet motors experience increased motor vibration noise due to local excessive magnetic flux density in the air gap, which worsens with higher torque density and output, canceling out size reduction advantages.
Innovation Solution
A permanent magnet motor design featuring a rotor core with strategically placed slits in the field pole, where the slit intervals gradually widen towards the outer peripheral side, disrupting the magnetic flux and reducing electromagnetic excitation forces, while maintaining high torque density and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an IPM motor is used to increase torque density and reduce size, then output and compactness are improved, but local excessive magnetic flux density in the air gap increases causing vibration noise
Solution Approach 1:
The rotor core is segmented by providing multiple slits that radially penetrate the rotor core at different angular positions. These slits divide the continuous rotor core into multiple segments, interrupting the magnetic flux path and preventing local excessive magnetic flux density concentration in the air gap, thereby reducing vibration noise while maintaining high torque density
Solution Approach 2:
Slits are provided at specific local positions on the rotor core surface rather than uniformly across the entire rotor. The slits are strategically placed to interrupt magnetic flux paths where local excessive flux density occurs, allowing the rotor to maintain high magnetic permeability and torque density in non-slit regions while reducing vibration noise at targeted locations
2Object-affected harmful factors
If slits are provided in the rotor core to reduce vibration noise, then magnetic flux density distribution is improved, but rotor strength and structural integrity may be compromised
Solution Approach 1:
Instead of providing slits across the entire rotor core circumference, slits are provided only at specific partial positions where local excessive magnetic flux density occurs. This partial action is sufficient to interrupt problematic flux paths and reduce vibration noise while preserving the structural integrity and strength of the rotor core in non-slit regions
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 effectively restricts vibration noise and torque ripple, allowing for a compact motor with increased output suitable for electric power steering systems without increasing the motor's physical structure.
Implementation Method 1
a permanent magnet 25 disposed in the rotor core 23... a stator winding 5... a stator core 3... transform electrical energy to mechanical energy
Implementation Method 2
a slit 41... disrupting the magnetic flux and reducing electromagnetic excitation forces... local excessive magnetic flux density in the air gap
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A permanent magnet motor such that a worsening of motor vibration noise is restricted is obtained. A permanent magnet motor (1) includes a stator (12), and a rotor (22) having a rotor core (23) disposed opposing an inner side of the stator (12) across an air gap (50), a permanent magnet (25) disposed in a circumferential direction of the rotor core (23), and a field pole (40) of the rotor core (23) in which the permanent magnet (25) is disposed, wherein the field pole (40) has a radius smaller than an arc centered on a shaft (24) attached to an inner side of the rotor (22), a multiple of a slit (41) whose longitudinal axial direction is a radial direction of the rotor core (23) are formed in the field pole (40), and an interval between a first central line (42a) positioned between a multiple of the slit (41) and a second central line (42b) positioned between a neighboring multiple of the slit (41) is enlarged as the first central line (42a) and the second central line (42b) head toward an outer peripheral side of the rotor core (23).