Rotor Lamination Surface Alloying for High-Speed Cavity Strength

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Solution Overview

Problem

Rotors for electric machines face challenges in achieving optimal performance and high operating speeds due to the need for structural support around internal cavities, which increases with higher speeds, and modifying cavity designs is not preferred.

Innovation Solution

Surface alloying and induction heating are used to strengthen structural members of the rotor laminations, specifically applying an austenite former material through induction heating to penetrate and harden bridges around the cavities, reducing the need for additional structural support and enhancing mechanical integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If structural support is increased around cavities to enable high-speed operation, then rotor strength and durability are improved, but rotor mass and manufacturing complexity increase

Engineering Contradiction:

Improverotor strengthVSAvoidrotor mass

Core Design Contradiction:

StrengthVSWeight of moving object

Solution Approach 1:

The patent applies local quality by selectively strengthening only the critical structural members (bridges and struts) around the cavities through surface alloying and induction heating, rather than uniformly increasing the strength of the entire rotor. This localized treatment adds minimal mass while providing targeted reinforcement where mechanical stresses are highest during high-speed operation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates composite material structures by combining the base electrical steel laminations with surface-applied alloying materials (such as chromium, nickel, or manganese) that penetrate during induction heating. This forms a composite structure with a strengthened surface layer over the base material, providing enhanced strength-to-weight ratio in the critical structural members.

Inventive Principle:

Principle #40Composite materials

2Reliability

If additional structural members are added to support high-speed operation, then rotor durability is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improverotor durabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the physical and chemical parameters of the existing structural members through surface alloying and induction heating. By controlling the alloying material composition, heating temperature, and heating duration, the structural properties (strength, hardness, toughness) of the bridges and struts are modified to enhance durability without adding new components or complex assembly steps.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces mechanical reinforcement (adding more structural members) with a thermal-chemical process (induction heating and surface alloying). This substitution achieves the same durability improvement through material property modification rather than through additional mechanical structures, simplifying the overall manufacturing process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If cavity design is modified to reduce structural support needs, then manufacturing is simplified, but magnetic performance and operational characteristics are adversely affected

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidmagnetic performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent maintains the original cavity design to preserve magnetic performance while applying local quality enhancement to the structural members surrounding the cavities. The surface alloying and induction heating are selectively applied only to the bridges and struts, leaving the cavity geometry unchanged and thus preserving the intended magnetic flux distribution and operational characteristics.

Inventive Principle:

Principle #3Local quality

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 magnetic performance by reducing magnetic leakage, provides mechanical strengthening, and allows for mass reduction, lower piece costs, increased torque, and high-speed operation while maintaining durability.

Implementation Method 1

A current is applied to the inductor to heat the structural members, alloying the alloying material into the structural members

Methodology Applied

Scientific EffectInduction heating: Induction Heating

Implementation Method 2

An alloying material is applied to the lamination stack at the structural members... alloying the alloying material into the structural members

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS12074485B2Method of making a rotor for an electric machine and system thereof

Publication Date: 2024.08.27 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

A rotor for an electric machine includes strengthened structural elements effected through surface alloying and heating via an induction heating fixture. A rotor includes laminations formed to have internal cavities and structural members adjacent the cavities. A number of the laminations are stacked to form a lamination stack. An alloying material is applied to the lamination stack at the structural members. The lamination stack is placed in a fixture so that an inductor extends along the structural members and cooling elements extend through the cavities. A current is applied to the inductor to heat the structural members, alloying the alloying material into the structural members.