Rotor Core Lamination Structure for High-Speed Shaft Retention

Solution Overview

Problem

In rotating electric machines, the rotor shaft and rotor core can detach due to centrifugal force during high-speed rotation, and making the rotor core smaller than the shaft to prevent this can lead to damage.

Innovation Solution

The rotor core is made with laminated steel sheets having an inner diameter smaller than the outer diameter of the rotor shaft, with thinner inner edges that curve along the rotor shaft's octagonal outer surface, reducing stress and maintaining contact even at high speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If the inner diameter of the rotor core is made smaller than the outer diameter of the rotor shaft to prevent detachment, then the restraining force between rotor shaft and rotor core is improved, but the rotor core becomes easily damaged

Engineering Contradiction:

Improverestraining forceVSAvoidrotor core strength

Core Design Contradiction:

ForceVSStrength

Solution Approach 1:

The rotor core employs different thicknesses at different locations: the inner edge part (first thickness) is thinner to reduce stress concentration and prevent damage, while the outer edge part (second thickness) is thicker to maintain sufficient restraining force. This local differentiation resolves the contradiction between preventing detachment and avoiding damage.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The inner edge part of the rotor core is formed with a curved surface that follows the outer peripheral surface of the rotor shaft. This curvature allows the thinner inner edge to maintain continuous contact with the shaft, distributing stress evenly and preventing stress concentration at sharp corners, thus resolving the contradiction between reduced thickness and structural integrity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Strength

If the rotor core is made thinner to reduce stress, then the rotor core strength is improved, but the restraining force between rotor shaft and rotor core deteriorates

Engineering Contradiction:

Improverotor core strengthVSAvoidrestraining force

Core Design Contradiction:

StrengthVSForce

Solution Approach 1:

The rotor core employs different thicknesses at different locations: the inner edge part (first thickness) is thinner to reduce stress concentration and prevent damage, while the outer edge part (second thickness) is thicker to maintain sufficient restraining force. This local differentiation resolves the contradiction between preventing detachment and avoiding damage.

Inventive Principle:

Principle #3Local quality

3Force

If the outer peripheral surface of the rotor shaft is made polygonal to maintain restraining force, then the restraining force is improved, but stress concentrates at the corners causing rotor core deterioration

Engineering Contradiction:

Improverestraining forceVSAvoidstress concentration

Core Design Contradiction:

ForceVSObject-affected harmful factors

Solution Approach 1:

The inner edge part of the rotor core is formed with a curved surface that follows the outer peripheral surface of the rotor shaft. This curvature allows the thinner inner edge to maintain continuous contact with the shaft, distributing stress evenly and preventing stress concentration at sharp corners, thus resolving the contradiction between reduced thickness and structural integrity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

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 reduces stress on the rotor core while maintaining the restraining force between the rotor shaft and core, preventing detachment and damage during high-speed rotation.

Implementation Method 1

an inner edge part of each laminated steel sheet is made thinner than an outer edge part thereof, and the inner edge part abuts on an outer peripheral surface of the rotor shaft and is curved along the outer peripheral surface of the rotor shaft in the direction of the axis of rotation

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11750052B2Rotating electric machine rotor

Publication Date: 2023.09.05 TOYOTA JIDOSHA KK

AI summary

A rotating electric machine rotor according to the present disclosure includes: a rotor shaft extending in a direction of an axis of rotation; and a rotor core fixedly fitted to an outer circumference of the rotor shaft and formed of laminated steel sheets. Further, an inner diameter of the rotor core is smaller than an outer diameter of the rotor shaft. Furthermore, an inner edge part of each laminated steel sheet is made thinner than an outer edge part thereof, and the inner edge part abuts on an outer peripheral surface of the rotor shaft and is curved along the outer peripheral surface of the rotor shaft in the direction of the axis of rotation.