Rotor Bridge Area Hardening for Electromagnetic Machine
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Solution Overview
Problem
Electromagnetic machine rotors, particularly in interior permanent magnet motors, face challenges in balancing mechanical strength and magnetic permeability, as existing methods either compromise on magnetic properties or structural integrity when attempting to enhance the rotor's hardness and fatigue resistance.
Innovation Solution
A method of selectively hardening the bridge areas between electrical steel lamination portions, increasing their yield strength and ultimate tensile strength while reducing magnetic permeability only in those areas, thereby maintaining magnetic softness in other parts, using techniques like nitriding, nitrocarburizing, or peening, to create a locally hardened and magnetically hardened rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the entire electrical steel lamination is hardened to increase mechanical strength, then the rotor's fatigue resistance improves, but the magnetic permeability decreases across the entire rotor compromising magnetic performance
Solution Approach 1:
The patent applies local quality by selectively hardening only the bridge areas of the electrical steel lamination while leaving other regions unchanged. This is achieved through localized treatment methods such as selective shot peening, localized heat treatment, or selective electrochemical treatment, which modify the mechanical properties of specific regions without affecting the entire component. The bridge areas receive the hardening treatment to improve fatigue resistance, while the magnetic regions maintain their original soft magnetic properties for optimal magnetic performance.
2Speed
If the bridge area hardness is increased to improve fatigue resistance, then the rotor can operate at higher speeds, but the magnetic permeability at the bridge area decreases
Solution Approach 1:
The patent implements local quality by applying different properties to different regions: the bridge areas are hardened to enable high-speed operation and improve fatigue resistance, while the magnetic regions maintain their soft magnetic characteristics. This spatial differentiation of properties allows the rotor to operate at higher speeds without compromising the magnetic performance of the stator or rotor magnetic circuits.
3Strength
If selective hardening is applied to bridge areas, then mechanical strength increases at critical points, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality through selective hardening processes that target only the bridge areas. Methods such as selective shot peening using directed media streams, localized induction heating, or selective electrochemical treatment are employed. These techniques require precise control and positioning but maintain relatively simple overall manufacturing workflows, avoiding the need for completely complex multi-step processes while achieving the desired localized property modification.
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 approach enhances the rotor's fatigue resistance and mechanical strength at critical points without compromising magnetic performance, optimizing the rotor's operation at high speeds and improving power density in electromagnetic devices.
Implementation Method 1
hardening may include nitriding only the bridge area
Implementation Method 2
hardening may include nitrocarburizing only the bridge area
Implementation Method 3
hardening may include peening only the bridge area
Implementation Method 4
hardening may include impinging a plurality of ions with the contact surface at only the bridge area
Data Source
AI summary
A method of forming a rotor includes isolating a bridge area of an electrical steel lamination. The bridge area is disposed between a first portion of the electrical steel lamination and a second portion of the electrical steel lamination that is adjacent to the first portion. Each of the first portion, the second portion, and the bridge area has an initial hardness, and the electrical steel lamination has an initial magnetic permeability. After isolating, the method includes hardening only the bridge area so that the bridge area has a treated hardness that is greater than the initial hardness. Concurrent to hardening, the method includes decreasing the initial magnetic permeability at only the bridge area.