Stator Core Axial Restraint for Electric Machine

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Solution Overview

Problem

Conventional stator core manufacturing methods for electric rotating machines can lead to buckling of magnetic steel sheets due to variations in dimensions, causing excessive compressive stress and weakening the fixing force, which increases iron loss and potentially results in separation of the sheets.

Innovation Solution

Incorporating restraints on the axial side of the stator core, retained by the outer cylinder, to manage axial deformation caused by circumferential compressive stress, preventing buckling and allowing for reduced staking or welding points to minimize iron loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the outer cylinder is shrink-fitted on the stator core segments to fasten them together, then the stator core segments are securely fastened, but buckling of the magnetic steel sheets occurs due to excessive circumferential compressive stress

Engineering Contradiction:

Improvefastening force of outer cylinderVSAvoidaxial deformation of stator core segments

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

A restraint member is introduced as an intermediary component between the outer cylinder and the stator core segments. The restraint member has a U-shaped cross-section with open ends facing the axial direction, and it restrains axial deformation of the stator core segments when the outer cylinder is shrink-fitted, thereby preventing buckling of the magnetic steel sheets while maintaining the fastening force.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stability of the object's composition

If the number of staking spots or welding spots in the magnetic steel sheets is increased to prevent buckling, then the structural integrity is improved, but iron loss of the stator core is increased

Engineering Contradiction:

Improvefixing force of magnetic steel sheetsVSAvoidiron loss of stator core

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The restraint member serves as a mediator that provides axial support to the stator core segments during the shrink-fitting process. This external support prevents buckling of the magnetic steel sheets, allowing the use of fewer staking or welding spots, thereby reducing iron loss while maintaining structural integrity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If the dimensions of the magnetic steel sheets and outer cylinder vary, then manufacturing flexibility is improved, but the circumferential compressive stress becomes excessively large causing buckling

Engineering Contradiction:

Improvedimensional variations toleranceVSAvoidcircumferential compressive stress

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The restraint member provides beforehand cushioning by restraining axial deformation of the stator core segments before the outer cylinder is fully shrink-fitted. This pre-support compensates for dimensional variations in the magnetic steel sheets and outer cylinder, preventing excessive circumferential compressive stress and buckling.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

Effectively prevents buckling of magnetic steel sheets, maintains the structural integrity of the stator core, and reduces iron loss by minimizing the number of fixing points, thereby enhancing the magnetic characteristics and efficiency of the electric rotating machine.

Implementation Method 1

the outer cylinder is first heated, thereby causing the inner diameter of the outer cylinder to become greater than the outer diameter of the stator core

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

the outer cylinder is cooled at room temperature until the difference in temperature between the outer cylinder and the stator core segments becomes zero

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Implementation Method 3

the restraint is arranged on an axial side of the stator core and retained by the outer cylinder so as to restrain axial deformation of the stator core segments due to the fastening force of the outer cylinder

Methodology Applied

Scientific EffectMechanical constraint: Mechanical Force

Data Source

PatentUS8896189B2Stator for electric rotating machine and method of manufacturing the same

Publication Date: 2014.11.25 DENSO CORP

AI summary

A stator for an electric rotating machine includes a hollow cylindrical stator core, a stator coil, an outer cylinder, and at least one restraint. The stator core is comprised of a plurality of stator core segments that are arranged in the circumferential direction of the stator core to adjoin one another in the circumferential direction. The stator coil is mounted on the stator core. The outer cylinder is fitted on the radially outer surfaces of the stator core segments so as to fasten the stator core segments together. The restraint is arranged on an axial side of the stator core and retained by the outer cylinder so as to restrain axial deformation of the stator core segments due to the fastening force of the outer cylinder.