Insulation Paper Crease Design for Rotary Machine Slot

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Solution Overview

Problem

Insulation paper in rotary electric machines is prone to cracking due to stress from coil end portions, especially with the miniaturization of machines, where the curvature of coil end portions increases the likelihood of cracks occurring along creases formed during folding.

Innovation Solution

The insulation paper is designed with a crease positioned at a folding location but excluding both end portions, and optionally includes an adhesive layer with the crease extending beyond it, ensuring the crease is not on the end portions where stress is applied, thereby preventing crack formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a crease is provided from one end to the other end of the insulation paper to make it easy to fold, then the ease of folding is improved, but the reliability deteriorates due to high crack occurrence at the end portions

Engineering Contradiction:

Improveease of foldingVSAvoidcrack resistance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The crease is segmented into two parts: a first crease portion at the folding location where the curvature radius is smaller, and a second crease portion at the end portion where the curvature radius is larger. This segmentation allows the crease to provide folding functionality while reducing stress concentration at the end portion, thereby preventing crack initiation and propagation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The crease is designed with different curvature radii at different locations: a smaller curvature radius at the folding location to enable easy folding, and a larger curvature radius at the end portion to reduce stress concentration and prevent cracks. This local differentiation of geometric properties optimizes both folding ease and crack resistance.

Inventive Principle:

Principle #3Local quality

2Productivity

If the curvature of coil end portion is increased to achieve miniaturization of the rotary electric machine, then the productivity is improved, but the reliability deteriorates due to increased stress on the insulation paper

Engineering Contradiction:

Improveminiaturization capabilityVSAvoidcrack resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The insulation paper is designed with a specific crease configuration that anticipates and cushions against the stress caused by high-curvature coil end portions. The crease with varying curvature radius absorbs and distributes the stress, preventing crack initiation even when the coil end portion has high curvature required for miniaturization.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of operation

If the crease is positioned at the end portion of the insulation paper to facilitate folding, then the ease of operation is improved, but the strength deteriorates due to stress concentration at the end portion

Engineering Contradiction:

Improvefolding capabilityVSAvoidstress resistance

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10897173B2Insulation paper and stator of rotary electric machine

Publication Date: 2021.01.19 HONDA MOTOR CO LTD

AI summary

There is provided an insulation paper to be disposed between a slot formed in a stator core and a coil inserted into the slot. A crease is provided in advance at a folding position where the insulation paper is to be folded when disposed in the slot. The crease is provided in an area of the insulation paper excluding both end portions thereof.