Outer Rotor Motor Uneven Air Gap for Lower Torque Ripple
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Solution Overview
Problem
Traditional outer rotor motors with even air gaps suffer from poor use efficiency and high noise due to larger tooth-slot torque peak values and counter electromotive force waveform distortion, leading to increased tangential torque pulsation.
Innovation Solution
The design incorporates an uneven air gap between the stator tooth and permanent magnet rotor element, with a narrower middle section and wider ends, maintaining a high fundamental wave magnetic density while reducing harmonic wave torque and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an even air gap is used in the motor, then the motor structure is simple and easy to manufacture, but the tooth-slot torque peak value increases and counter electromotive force waveform distortion rate increases, resulting in higher tangential torque pulsation and greater noise
Solution Approach 1:
The patent applies asymmetry by designing an uneven air gap structure where the air gap distance varies around the stator circumference. Specifically, the air gap is smaller at certain positions and larger at others, creating an asymmetric distribution that modifies the magnetic field characteristics. This asymmetric design reduces the tooth-slot torque peak value and counter electromotive force waveform distortion rate, thereby lowering tangential torque pulsation and motor noise while maintaining manufacturing feasibility.
2Ease of manufacture
If an even air gap is used in the motor, then the manufacturing process is simplified, but the power density decreases due to higher torque pulsation and lower efficiency
Solution Approach 1:
The uneven air gap structure with asymmetric distribution optimizes the magnetic field to reduce torque pulsation and improve efficiency, leading to higher power density despite the slightly more complex manufacturing process compared to even air gaps.
3Power
If an uneven air gap with narrower middle section and wider ends is used, then power density increases and tooth-slot torque peak value decreases, but the air gap structure becomes more complex
Solution Approach 1:
The patent applies local quality by creating different air gap distances at different locations around the stator. The middle section has a narrower air gap while the ends have wider air gaps, optimizing the magnetic field distribution locally at each position. This localized optimization reduces tooth-slot torque peak value and improves power density without requiring complete structural redesign.
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 enhances power density and reduces vibration noise, improving flight stability in unmanned aerial vehicles by lowering tooth-slot torque peak values and counter electromotive force distortion rates.
Implementation Method 1
an air gap between an end surface of the stator tooth facing the permanent magnet rotor element and the permanent magnet rotor element is an uneven air gap
Implementation Method 2
counter electromotive force waveform distortion rate
Data Source
AI summary
The present disclosure discloses an outer rotor motor and an unmanned aerial vehicle apparatus. The outer rotor motor includes a rotor assembly and a stator assembly. The rotor assembly includes a plurality of permanent magnet rotor elements. The stator assembly includes a stator yoke and a plurality of stator teeth disposed in a circumferential direction of the stator yoke. An air gap is used to separate the rotor assembly and the stator assembly with a gap and in an air gap between an outer arc surface of the stator tooth facing the air gap and an inner arc surface of the permanent magnet rotor element facing the air gap. A gap of a middle section of the air gap is less than gaps of two ends of the air gap.