Electric Motor Rotor With Variable Magnet Thickness
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Solution Overview
Problem
Electric motors face challenges in suppressing cogging torque and heat buildup, especially at high rotation speeds, and require improved manufacturing processes for their rotors.
Innovation Solution
A rotor design featuring a sleeve, magnets, and a cylindrical reinforcing member, where the magnets have a central portion and end portions with reduced thickness forming gaps, are held between the sleeve and the reinforcing member, minimizing magnetic flux change and facilitating high-speed operation while simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnets are held tightly between the sleeve and reinforcing member, then reliability of magnet fixation is improved, but cogging torque increases due to increased magnetic flux change
Solution Approach 1:
The magnet is designed with different thicknesses in different regions: a thicker central portion for reliable fixation and thinner end portions to reduce magnetic flux change. This local quality differentiation allows the magnet to simultaneously achieve secure holding and reduced cogging torque.
Solution Approach 2:
The magnet is segmented into a central portion and end portions with different thickness characteristics. The central portion maintains full thickness for strong magnetic field and fixation, while the end portions are thinned to reduce flux leakage and cogging torque.
2Reliability
If magnets are held tightly between the sleeve and reinforcing member, then reliability of magnet fixation is improved, but heat build-up increases during operation
Solution Approach 1:
The magnet features a thick central portion for reliable fixation and thin end portions that reduce magnetic flux change. This local quality differentiation reduces eddy current losses and heat generation at the magnet ends while maintaining secure holding through the central portion.
3Object-generated harmful factors
If the gap between the sleeve and magnet end portion is made larger, then cogging torque is reduced, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The magnet is pre-formed with a specific thickness distribution (thinner end portions) before assembly. This preliminary action ensures that the gap between the magnet end portions and sleeve is automatically controlled within a desired range, simplifying manufacturing while achieving reduced cogging torque.
Solution Approach 2:
The magnet thickness parameter is varied across different regions, with end portions having reduced thickness compared to the central portion. This parameter change creates the desired gap without requiring tight dimensional control during assembly.
4Object-generated harmful factors
If the magnet thickness is reduced at end portions, then cogging torque and heat are reduced, but manufacturing complexity increases
Solution Approach 1:
The magnet thickness parameter is systematically varied across different regions. The end portions have reduced thickness compared to the central portion, creating the necessary gap while maintaining ease of manufacture through standardized forming processes.
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 effectively reduces cogging torque and heat generation, enables high-speed applications, and streamlines the manufacturing process by maintaining gap integrity and uniform force distribution.
Implementation Method 1
forming a gap between the sleeve and the end portion... restraint of generation of cogging torque
Implementation Method 2
cylindrical reinforcing member surrounding the plurality of magnets so as to contact with outer surfaces of the plurality of magnets, and holding the plurality of magnets between the sleeve and the reinforcing member
Data Source
AI summary
A rotor capable of suppressing cogging torque and heat build-up caused when an electric motor is operated. The rotor includes a sleeve fixed to a radially outside of a rotary shaft, a plurality of magnets disposed around a radially outside of the sleeve, and a reinforcing member having a cylindrical shape that surrounds the plurality of magnets while being in contact with an outer surface of each of the plurality of magnets to hold the plurality of magnets with the sleeve, each of the plurality of magnets including a central portion in a circumferential direction, in contact with the sleeve, and an end portion in the circumferential direction, having a thickness less than that of the central portion and forming a gap with the sleeve.