Electric Motor Rotor Groove Angle Optimization
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Solution Overview
Problem
Conventional electric motors experience significant torque ripple and noise issues due to the design of the rotor and stator configuration, particularly with the angle and depth of grooves and protrusions, which affect the efficiency and vibration characteristics.
Innovation Solution
The electric motor design incorporates a rotor with a permanent magnet and a stator core featuring annular shape with tooth portions and a groove portion on the rotor's outer circumference, where the angle between the groove bottom point and the magnetic pole center is between 30% to 47% of an electric angle of 90 degrees, and the stator protrusions have a narrower width at the inside radial direction than the outside, optimizing the placement of wound coils and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the groove depth and angle in the rotor outer circumference are increased to reduce torque ripple, then the vibration and noise characteristics are improved, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies parameter changes by optimizing the groove depth ratio (0.05 to 0.15 times the rotor outer radius) and groove angle (10 to 30 degrees) to suppress torque ripple. This resolves the contradiction by finding specific parameter values that achieve vibration reduction without excessive structural complexity
Solution Approach 2:
The patent applies local quality by creating asymmetric groove structures at specific locations on the rotor outer circumference, with different groove depths and angles in different regions. This localized optimization reduces torque ripple while maintaining overall structural simplicity
2Manufacturing precision
If the stator protrusion width is reduced at the inner radial direction to optimize coil placement, then the manufacturing precision is improved, but the strength and structural integrity may be compromised
Solution Approach 1:
The patent applies local quality by creating asymmetric stator protrusions where the width varies in the radial direction - narrower at the inner radial direction for precise coil placement and wider at the outer radial direction for structural strength. This resolves the contradiction by optimizing different regions for different functions
Solution Approach 2:
The patent applies asymmetry by designing stator protrusions with different widths at different radial positions, creating an asymmetric cross-sectional shape that simultaneously achieves precise coil placement capability and sufficient structural integrity
3Object-affected harmful factors
If the groove angle is optimized to reduce noise, then the vibration characteristics are improved, but the device complexity increases due to precise angular requirements
Solution Approach 1:
The patent applies parameter changes by specifying the groove angle within the range of 10 to 30 degrees, which optimizes noise reduction while providing a practical manufacturing range that doesn't require excessive angular precision
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 torque ripple and noise, enhancing the motor's vibration and noise characteristics, particularly in hybrid vehicles, by optimizing the angle and dimensions of the groove and protrusion features.
Implementation Method 1
The rotor includes a permanent magnet
Implementation Method 2
The stator core is formed in an annular shape enclosing the rotor and includes a plurality of tooth portions projecting toward the rotor
Data Source
AI summary
An electric motor includes a rotor and a stator core. The rotor has an outer circumferential wall around a rotational axis. The rotor includes a magnet and a groove. The magnet has a magnetic pole center. The groove is provided in the outer circumferential wall to be recessed toward the rotational axis to have a bottom point. An angle between a first virtual line connecting the bottom point of the groove and the rotational axis and a second virtual line connecting the magnetic pole center and the rotational axis viewed along the rotational axis is from 30% to 47% of an electric angle of 90 degrees. The stator core includes an inner circumferential wall. The stator core includes teeth projecting from the inner circumferential wall toward the stator axis. A cross-sectional shape of each teeth includes a first protrusion and a second protrusion.