Stator Core Stiffness Tuning for BLDC Motor Noise Mitigation
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Solution Overview
Problem
Brushless direct current electric motors resonate at frequencies (2500 Hz to 3500 Hz) that are perceptible to the human ear, causing unwanted noise, which existing designs fail to effectively mitigate.
Innovation Solution
The motor design includes a stator core with a ring and teeth, where various sound mitigating features such as added or reduced material portions, alternating stiff and flexible portions, and compressive forces are applied to shift the natural frequency of the motor outside the sensitive frequency range, reducing human perceptible sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the motor operates at its natural frequency, then the motor generates vibrations, but the vibrations fall within the human ear's sensitive frequency range (2500 Hz to 3500 Hz) causing perceptible noise
Solution Approach 1:
The patent applies parameter changes by modifying the stiffness of the stator core through circumferential compression, which shifts the natural frequency of the motor from the human-sensitive range (2500-3500 Hz) to a higher frequency range. This changes the physical parameter of the stator core (stiffness) to achieve the desired frequency shift and reduce perceptible noise.
Solution Approach 2:
The patent utilizes mechanical vibration principles by applying circumferential compression forces to the stator core, which modifies the vibrational characteristics of the motor. The compression alters the natural frequency of vibration, moving it away from the human ear's sensitive range, thereby reducing perceptible noise while maintaining operational vibrations.
2Object-affected harmful factors
If compressive force is applied to the stator core to shift natural frequency, then perceptible noise is reduced, but the structural integrity and manufacturing complexity increase
Solution Approach 1:
The patent applies local quality by implementing circumferential compression specifically at the stator core region, rather than uniformly across the entire motor. This localized approach targets the source of the noise problem (the stator core's natural frequency) while minimizing overall structural complexity and manufacturing complexity of the motor.
Solution Approach 2:
The patent introduces an intermediary mechanism (the compression apparatus or pre-compression structure) that applies force to the stator core to shift its natural frequency. This intermediary element enables the frequency adjustment without requiring fundamental redesign of the entire motor structure, thereby managing device complexity while achieving noise reduction.
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 solution effectively reduces the perceived noise by shifting the natural frequency of the motor, making the vibrations less noticeable to the human ear, with potential sound reductions of up to 5 dB.
Implementation Method 1
Stiffness is often defined as the extent to which an object resists deformation in response to an applied force. Natural frequency of a mass-spring system is the frequency at which the system would oscillate if there were no driving force and no damping force. Natural frequency is dependent on both the mass of the object and the stiffness of the spring.
Implementation Method 2
The shifting means is also configured to apply a compressive force to the ring of the stator core.
Data Source
AI summary
A motor includes a rotor having magnets therein and a stator. The stator includes a stator core having a ring and a plurality of teeth extending from the ring, a plurality of coils wrapped around the plurality of teeth, and a means for shifting a natural frequency of the motor to a frequency value outside a range of 2500 Hertz (Hz) to 3500 Hz.