EC Motor Back Iron with Alternating Thickness for Braking Torque
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Solution Overview
Problem
Electronically commutated direct current motors with non-ferrous stator windings face limitations in achieving sufficient braking torque due to cogging torque issues, which are exacerbated by varying magnetic conductivities and air gap widths, particularly in compact applications like roller blinds and medication dispensing units where uncontrolled rotor rotations can lead to incorrect dosing.
Innovation Solution
The magnetically conductive back iron is reshaped with alternating thicknesses and geometries, featuring a cylindrical shell surface on one circumference and an alternating tooth-like geometry on the other, or a combination thereof, to optimize braking torque without increasing motor size or weight, and can be manufactured using laminated core assemblies via die cutting or laser cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the back iron is given an alternating thickness design to reduce weight, then the weight of the motor is reduced, but the magnetic field distribution becomes non-uniform causing increased cogging torque
Solution Approach 1:
The back iron is designed with locally varying thicknesses in specific angular ranges to reduce weight in those areas, while maintaining sufficient thickness in other areas to ensure uniform magnetic field distribution and minimize cogging torque. This selective local modification allows weight reduction without compromising overall magnetic field uniformity.
Solution Approach 2:
The back iron employs an asymmetric thickness distribution pattern that is optimized for both weight reduction and magnetic field uniformity. The asymmetric design allows different thicknesses in different angular positions, creating a configuration that balances weight savings with cogging torque minimization through careful geometric arrangement.
2Volume of moving object
If the motor size is reduced for compact applications, then the motor fits better in narrow tubes, but the braking torque becomes insufficient
Solution Approach 1:
The invention changes the geometric parameters of the back iron, specifically the alternating thicknesses in different angular ranges, to optimize the magnetic field distribution. This parameter optimization enhances the braking torque generation capability within the compact motor volume, allowing sufficient braking force without increasing overall motor size.
Solution Approach 2:
The back iron is segmented into multiple angular ranges with different thicknesses, creating a multi-zone structure that optimizes magnetic field distribution throughout the motor. This segmentation allows the compact motor to generate adequate braking torque by strategically distributing magnetic conductive material across different angular sectors.
3Adaptability or versatility
If the back iron thickness is varied to optimize braking torque, then the braking torque becomes controllable, but the manufacturing complexity increases
Solution Approach 1:
The back iron design employs parameter variations in thickness that are optimized for braking torque control while remaining compatible with standard manufacturing processes. The geometric parameters are selected to achieve controllable braking torque through conventional forming and machining techniques, balancing performance optimization with manufacturing feasibility.
Solution Approach 2:
The back iron serves multiple functions simultaneously: it provides structural support, optimizes magnetic field distribution for weight reduction, and enables controllable braking torque through its alternating thickness design. This multi-functionality is achieved through a universal geometric configuration that integrates these diverse requirements into a single manufacturable component.
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 design significantly enhances braking torque variability with a reduced number of parts, eliminating the need for additional components and ensuring stable rotor operation across different applications by optimizing magnetic field distribution and air gap widths.
Implementation Method 1
This design significantly enhances braking torque variability with a reduced number of parts, eliminating the need for additional components and ensuring stable rotor operation across different applications by optimizing magnetic field distribution and air gap widths.
Implementation Method 2
Because the magnetically conductive back iron has different magnetic conductivities over its circumference, a cogging torque develops, and thus a braking or holding torque during standstill of the rotor.
Implementation Method 3
The magnetically conductive back iron is reshaped with alternating thicknesses and geometries, featuring a cylindrical shell surface on one circumference and an alternating tooth-like geometry on the other, or a combination thereof, to optimize braking torque without increasing motor size or weight
Data Source
AI summary
An electronically commutated direct current motor made up of a cylindrically shaped non-ferrous stator winding; a cylindrically shaped, magnetically conductive back iron arranged radially outside of the stator winding; and a cylindrically shaped permanent magnet rotor arranged concentrically within the stator winding, wherein the magnetically conductive back iron has different magnetic conductivities over its circumference.