Split Stator Core with Magnetic Straddling for Cogging Torque Reduction
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Solution Overview
Problem
Miniaturization of electric motors is hindered by increased cogging torque and reduced rigidity due to manufacturing variations and misalignment of stator cores, particularly when an annular sleeve is disposed outside the stator core, leading to a larger outer diameter and low radial and axial rigidity.
Innovation Solution
The electric motor stator incorporates a split stator structure with stator core parts having a core back portion and tooth portions, covered by insulators with magnetic substances placed between the core back portions and insulators to straddle adjacent stator core parts, reducing magnetic resistance and improving rigidity by forming a parallel magnetic circuit, thus minimizing cogging torque and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an annular sleeve is disposed outside the stator core to reduce cogging torque, then cogging torque due to manufacturing variation is reduced, but the outer diameter of the stator increases
Solution Approach 1:
The magnetic substance is nested within the stator core structure, specifically disposed between the core back portions and insulators, rather than adding an external annular sleeve. This nesting approach allows the cogging torque reduction function to be integrated into the existing stator geometry, reducing cogging torque without increasing the outer diameter of the motor.
2Length of stationary object
If the annular sleeve is thinned and stator pieces are joined to achieve miniaturization, then the outer diameter is reduced, but rigidity in radial and axial directions becomes low
Solution Approach 1:
The stator core is constructed as a composite structure combining multiple materials: magnetic substances (such as magnetic steel sheets or SMC) for the core back portions, non-magnetic substances (such as resins or metals) for the insulators and structural support, and reinforcing ribs. This composite construction provides both the miniaturization needed for compact size and the enhanced rigidity required for radial and axial strength.
3Productivity
If a plurality of divided stator cores are annularly combined to form a stator core, then winding space factor is improved, but misalignment of abutting portions occurs and magnetic characteristics deteriorate
Solution Approach 1:
Non-magnetic substance insulators are introduced as intermediary elements between the adjacent stator core parts made of magnetic substance. These insulators serve as positioning references that facilitate precise alignment of the abutting portions during assembly, eliminating misalignment issues while maintaining the benefits of the divided stator core structure for improved winding space factor.
4Object-affected harmful factors
If magnetic substances are disposed between core back portions and insulators to straddle adjacent stator core parts, then cogging torque is reduced and rigidity is improved, but manufacturing complexity increases
Solution Approach 1:
The magnetic substances serving as cogging torque reduction elements are merged with the core back portions of the stator core parts, forming an integrated structure. The core back portions are themselves designed to serve as positioning references for assembly, combining multiple functions (structural support, magnetic flux path, and alignment reference) into unified components, thereby reducing manufacturing complexity despite the advanced functionality.
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 reduces cogging torque and vibration while maintaining a compact size by enhancing the stator's radial and axial rigidity, suppressing the increase in outer diameter and improving motor output.
Implementation Method 1
a plurality of magnetic substances are provided between inner peripheral ends of the core back portions and the insulators in such a way as to straddle the core back portions of the stator core parts that are adjacent
Implementation Method 2
reducing magnetic resistance and improving rigidity by forming a parallel magnetic circuit
Data Source
AI summary
A stator of an electric motor includes: a stator core including a plurality of joined stator core parts each having a core back portion and a tooth portion; a plurality of insulators covering a plurality of the tooth portions; coils wound around the tooth portions via the insulators; and a plurality of magnetic substances provided between inner peripheral ends of the core back portions and the insulators in such a way as to straddle the core back portions of the stator core parts that are adjacent.