Washing Machine SPMSRotor Pole Configuration for Cogging Torque Noise
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Solution Overview
Problem
Existing surface permanent magnet synchronous motors (SPMSMs) in washing machines generate undesirable noise due to cogging torque, which is exacerbated by manufacturing gaps and unclear causes of noise, particularly at high rotation speeds.
Innovation Solution
The motor incorporates an annular magnetic pole body with a combination of two or more types of magnets with different numbers of magnetic poles, which are arranged in a circumferential direction, which are arranged in a circumferential direction, and the rotor includes magnets with arc-shaped cross-sections, reducing the number of magnets and distributing harmonic components of cogging torque by using magnets with different magnetic poles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a surface permanent magnet synchronous motor is used to achieve wide rotation speed range, then the motor can operate from low speed (45 RPM) during washing to high speed (1200 RPM) during spinning, but noise generated by the motor at high rotation speeds becomes undesirably loud
Solution Approach 1:
The patent changes the magnetic pole configuration parameter by using an annular magnetic pole body with magnets having different numbers of magnetic poles (e.g., 12 poles and 10 poles) instead of uniform magnets. This parameter change redistributes the magnetic field harmonics, suppressing cogging torque and reducing noise at high rotation speeds while maintaining the wide speed range capability
Solution Approach 2:
The patent employs a composite magnetic pole structure combining different types of magnets (with different pole counts) in an annular arrangement. This composite configuration creates a non-uniform magnetic field distribution that cancels out harmful harmonic components, thereby reducing noise without compromising the motor's speed range performance
2Object-affected harmful factors
If the shape of magnets or core is designed differently to suppress cogging torque, then noise may be reduced, but manufacturing precision requirements increase and small gaps during manufacturing still cause noise
Solution Approach 1:
The patent converts the potentially harmful effect of manufacturing gaps into a beneficial feature by designing the annular magnetic pole body with magnets of different pole counts. The inherent imperfections and gaps in mass production are accommodated by the distributed pole configuration, which naturally suppresses harmonics and reduces noise sensitivity to manufacturing tolerances
Solution Approach 2:
By changing the magnetic pole configuration to include magnets with different numbers of poles arranged in an annular pattern, the patent creates a magnetic field distribution that is inherently more robust to manufacturing variations. This parameter change reduces the system's sensitivity to small gaps and positioning errors during manufacturing
3Object-affected harmful factors
If magnets with different numbers of magnetic poles are arranged in an annular magnetic pole body, then harmonic components of cogging torque are suppressed and noise is reduced, but the device complexity increases
Solution Approach 1:
The patent segments the magnetic pole body into multiple independent magnet units with different pole counts arranged in an annular configuration. This segmentation allows each magnet type to contribute differently to the overall magnetic field, suppressing harmonics while maintaining a relatively simple integrated structure that can be manufactured as a single rotor assembly
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 effectively suppresses harmonic components of cogging torque, reducing noise and vibration, even with magnetization imbalance, and allows for high-speed rotation without additional damping materials.
Implementation Method 1
a motor configured to rotate the rotary tub. According to an embodiment of the disclosure, the motor of the washing machine may include a rotor configured to rotate about a rotation axis. According to an embodiment of the disclosure, the motor of the washing machine may include a stator configured to face the rotor with an air gap therebetween
Implementation Method 2
the rotor may include an annular magnetic pole body in which a plurality of magnets having an arc-shaped cross-section are arranged in a circumferential direction of the rotor
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Disclosed is a washing machine including a motor for suppressing an increase in the harmonic components of cogging torque even if magnetization unbalance occurs. The motor of the washing machine includes: a rotor rotating around a rotary shaft; and a stator facing the rotor with an air gap interposed therebetween, wherein the rotor includes an annular magnetic pole body in which a plurality of magnets having an arc-shaped cross section are disposed in the circumferential direction of the rotor, and the annular magnetic pole body includes at least two types of magnets having different numbers of magnetic poles.