Stator Core Segment Assembly via Axial Caulking

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Solution Overview

Problem

The existing stator core assembly techniques for rotating electric machines face challenges with poor assemblability, degraded positioning accuracy, and buckling due to low rigidity, particularly when the stator core segments are subjected to stress from an outer casing during shrink fitting.

Innovation Solution

The stator core design incorporates specific caulking sites in the yoke part, including a second caulking site at the center between teeth and a third caulking site near the yoke junction, with these sites formed on arcs passing through the central part of the radial length, enhancing the assembly process and improving the rigidity and positioning accuracy of the stator core segments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the protrusion is pressed and fitted into the recess formed in a yoke part, then the stator core segments are coupled together, but pressurization in the circumferential direction is required resulting in poor assemblability

Engineering Contradiction:

Improvecoupling of stator core segmentsVSAvoidassemblability

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

Instead of pressing the protrusion into the recess in the conventional circumferential direction, the invention inverts the assembly approach by pressing the stator core segments in the axial direction. The caulking sites are formed on the outer circumferential surface facing the shrink-fitting outer casing, allowing the outer casing to apply pressure axially to secure the segments, eliminating the need for difficult circumferential pressurization.

Inventive Principle:

Principle #13The other way round (Inversion)

2Stability of the object's composition

If shrink fitting is carried out from the outer circumferential side, then the stator core segments are secured to form a cylindrical stator core, but a stress in the radially inward direction acts on the segments causing degraded positioning accuracy and buckling

Engineering Contradiction:

Improvecircularity of stator coreVSAvoidpositioning accuracy of stator core segments

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The invention applies local quality by forming caulking sites at specific locations on the outer circumferential surface of the yoke part. These localized reinforced areas face the outer casing and provide targeted support where the shrink-fitting stress is applied, preventing general buckling and maintaining positioning accuracy under radially inward stress.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The caulking sites are formed in advance on the outer circumferential surface before the shrink-fitting process. This preliminary reinforcement structure prepares the stator core segments to withstand the upcoming radially inward stress from the outer casing, preventing deformation and maintaining positioning accuracy during the assembly process.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If shrink fitting is carried out from the outer circumferential side, then the stator core segments are secured, but stress in the radially inward direction causes buckling due to low rigidity

Engineering Contradiction:

Improvesecuring of stator core segmentsVSAvoidrigidity of stator core segments

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The caulking sites create localized regions of increased rigidity on the outer circumferential surface. These reinforced areas are strategically positioned to face the outer casing, providing structural support exactly where the shrink-fitting stress is applied, thereby preventing buckling without requiring a complete redesign of the entire segment structure.

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 design allows for easier assembly and improved positioning accuracy of stator core segments, reducing the likelihood of buckling and enhancing the overall circularity and rigidity of the stator core, thereby addressing the issues of assemblability and stress-induced deformation.

Implementation Method 1

an outer casing is shrink fitted with the stator core segments being arranged annularly, so that the stator core segments are secured to form a cylindrical stator core

Methodology Applied

Scientific EffectShrink fitting: Thermal Contraction

Data Source

PatentEP2523309B1Stator core

Publication Date: 2019.09.04 TOYOTA JIDOSHA KK

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AI summary

A stator core capable of improving Stator core segments in assemblability, positioning accuracy and rigidity is provided. A stator core (141) includes a plurality of stator core segments (175), and a yoke part (176) of each stator core segment (175) has a first junction (178) and a Second junction (179) joined to other adjacent Stator core segments. A protrusion (193) is formed at the first junction (178), and a recess (196) capable of receiving the protrusion (193) is formed at the Second junction (179). The opening area of the recess (196) increases from a deepest section (196b) of the recess, (196) to an opening (196a) of the recess (196). In the yoke part (176), a first caulking site (187) where the stator core segment (175) is caulked in an axial direction (DR1) is formed on an arc passing through the central part of a radial length (r4) of the protrusion (193) and extending in a circumferential direction (DR2).