Washing machine including surface permanent magnet synchronous motor
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Solution Overview
Problem
Surface permanent magnet synchronous motors (SPMSMs) in washing machines experience noise due to cogging torque, particularly at high rotation speeds, which is exacerbated by manufacturing gaps and magnetization imbalances, leading to increased harmonic components of cogging torque.
Innovation Solution
The motor design incorporates an annular magnetic pole body with a combination of magnets having different numbers of magnetic poles, arranged in a circumferential direction, to distribute the force acting on each magnetic pole and cancel out harmonic components, even in the presence of magnetization imbalances, thereby reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a surface permanent magnet synchronous motor is used to rotate the washing tub, then the motor can operate over a wide range of rotation speeds from low speed during washing to high speed during spinning, but noise generated by the motor at high rotation speeds becomes undesirably loud
Solution Approach 1:
The rotor is divided into multiple magnetic pole bodies, each with a specific number of magnets. By segmenting the magnetic pole bodies into different groups (first, second, third) with different numbers of magnets, the patent creates a segmented structure that reduces cogging torque harmonics and suppresses noise at high rotation speeds while maintaining the wide speed range operation capability
Solution Approach 2:
Different regions of the rotor are assigned different local qualities through the use of magnetic pole bodies with different numbers of magnets. The first magnetic pole body has a different number of magnets compared to the second and third magnetic pole bodies, creating local variations in magnetic properties that reduce overall cogging torque and noise while preserving the motor's wide speed range performance
2Object-affected harmful factors
If the cogging torque is suppressed by designing the shape of magnet or core differently, then noise may be reduced, but in mass-produced SPMSMs, noise may still be caused due to small gaps during manufacturing and the cause for noise becomes unclear
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-compensating for manufacturing variations in the motor design phase. By designing the magnetic pole bodies with specific numbers of magnets that inherently reduce cogging torque sensitivity to manufacturing gaps, the system proactively addresses potential noise issues before they occur in mass production, making the design robust against manufacturing tolerances
Solution Approach 2:
The patent converts the harmful effect of manufacturing gaps into a benefit by designing a magnetic pole structure where the presence of multiple magnetic pole bodies with different magnet counts creates a self-compensating system. The variations in magnet numbers across different pole bodies cause the cogging torque variations due to manufacturing gaps to average out, transforming the potential harm of manufacturing imprecision into a robust design feature
3Object-affected harmful factors
If magnets with different numbers of magnetic poles are arranged in the annular magnetic pole body, then harmonic components of cogging torque can be suppressed, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by varying the number of magnets in different magnetic pole bodies rather than changing the physical dimensions or materials. This parameter variation approach reduces cogging torque harmonics while maintaining relatively simple manufacturing processes, as it only requires changing the count of standard magnets rather than redesigning the entire magnetic structure
Solution Approach 2:
The rotor employs a composite magnetic structure consisting of multiple magnetic pole bodies with different numbers of magnets. This composite configuration combines the advantages of different magnet arrangements to achieve reduced cogging torque harmonics while maintaining a manageable level of structural complexity through systematic arrangement of the magnetic components
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 the increase in harmonic components of cogging torque, resulting in reduced noise and improved operational efficiency, even during high-speed rotations.
Implementation Method 1
a motor configured to rotate the rotary tub... the rotor may include an annular magnetic pole body in which a plurality of magnets having an arc-shaped cross-section are arranged
Implementation Method 2
surface permanent magnet synchronous motors (SPMSM)... the rotor may include an annular magnetic pole body in which a plurality of magnets having an arc-shaped cross-section are arranged
Data Source
AI summary
Provided is a washing machine including a motor configured to suppress an increase in a harmonic component of cogging torque even when a magnetization imbalance occurs. The motor of the washing machine may include a rotor configured to rotate about a rotation axis, and a stator facing the rotor with an air gap therebetween, wherein the rotor includes 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, and the annular magnetic pole body includes two or more types of magnets having different numbers of magnetic poles.