Stator Core Groove Positioning Accuracy via Segmented Stamping

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Solution Overview

Problem

The existing methods for manufacturing stator cores, such as split and straight cores, face challenges in maintaining dimensional accuracy of recesses used for positioning, leading to decreased positioning accuracy and increased cogging torque and torque ripple in motors due to potential distortions in the magnetic path.

Innovation Solution

A method where individual pieces including core back and tooth portions are stamped out from an electromagnetic steel sheet, with the groove portion formed by punching, and the entire plate member is stamped out in a single step, using the groove portion as a reference to ensure precise positioning and accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If plate members are stamped out from electromagnetic steel sheet using conventional stamping method, then manufacturing simplicity is maintained, but dimensional accuracy of groove portions decreases

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoiddimensional accuracy of groove portions
Core Design Contradiction:
Ease of manufactureVSManufacturing precision

Solution Approach 1:

The stamping process is segmented into two distinct steps: first forming the groove portions by punching, then stamping out the individual pieces. This segmentation allows the groove portions to be formed with high dimensional accuracy using punching, while the subsequent stamping step completes the plate member formation. The groove portions serve as reference features that maintain their accuracy throughout the process.

Inventive Principle:
Principle #1Segmentation

2Manufacturing precision

If dimensional accuracy of groove portions decreases, then positioning accuracy of split cores decreases, but manufacturing complexity increases

Engineering Contradiction:
Improvepositioning accuracyVSAvoidmanufacturing process complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The groove portions are formed in advance by punching before the individual pieces are stamped out. This preliminary action ensures that the positioning features are created with high dimensional accuracy first, and then the rest of the plate member is formed. The groove portions serve as pre-established reference features for subsequent positioning operations.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3312976B1Stator core manufacturing method, stator core inspection method, stator core, and motor
Publication Date: 2021.03.31 NIDEC CORP(JP)
  • EP3312976B1 patent drawingFigure 1
  • EP3312976B1 patent drawingFigure 2
  • EP3312976B1 patent drawingFigure 3

AI summary

A method of manufacturing a stator core, the stator core that includes core pieces arranged in a circumferential direction about a central axis that extends in an up-down direction, the core pieces formed by stacking plate members, the plate members each including a core back portion extending in the circumferential direction, a tooth portion extending from the core back portion towards a first side in a radial direction, and a groove portion recessed from a surface on a second side of the core back portion in the radial direction towards the first side in the radial direction, the method of manufacturing the stator core including stamping out an individual piece including the core back portion and the tooth portion stamped out from an electromagnetic steel sheet, and forming the groove portion formed by punching a portion of the electromagnetic steel sheet.