Stator Assembly Shrink Fitting Stress Distribution
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Solution Overview
Problem
Existing electric motor stator assemblies experience non-uniform circumferential stress when assembled using interference fitting processes, which can lead to motor housing damage and breakage due to uneven stress distribution.
Innovation Solution
The stator assembly design incorporates alternating projecting and stopper portions with specific curvature radii and a shift angle, ensuring uniform stress distribution by adjusting the curvature radii of the projecting and stopper portions to prevent inhomogeneous stress on the motor housing, thereby minimizing the risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stator is assembled to the motor housing by interference fitting process, then the stator is firmly fixed to the motor housing, but non-uniform circumferential stress is applied to the motor housing which may cause damage and breakage
Solution Approach 1:
The stator's outer peripheral surface is divided into multiple contacting areas and non-contacting areas along the circumferential direction. This segmentation allows the interference fitting stress to be distributed across multiple discrete contacting areas rather than concentrated uniformly, reducing peak stress values and preventing motor housing damage while maintaining firm fixation.
Solution Approach 2:
Different regions of the stator's outer peripheral surface are given different properties: contacting areas are designed to engage with the motor housing to provide fixation, while non-contacting areas are designed to avoid contact to reduce stress concentration. This local differentiation optimizes both fixing strength and stress distribution.
2Strength
If projecting portions are provided on the stator to contact the motor housing, then fixation is achieved, but tensile stress in circumferential direction is applied to the motor housing which may become larger and cause damage
Solution Approach 1:
The projecting portions are segmented into multiple discrete areas around the circumferential direction rather than forming a continuous ring. This segmentation reduces the total circumferential tensile force by distributing it across multiple smaller contact points, preventing excessive stress accumulation that could damage the motor housing.
Solution Approach 2:
Instead of providing continuous contacting areas around the entire circumference, only partial contacting areas are provided. This partial action achieves sufficient fixation strength while avoiding the excessive circumferential tensile stress that would result from complete circumferential contact.
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 effectively uniformalizes the circumferential stress applied to the motor housing, enhancing its durability and extending the operational temperature range by reducing the risk of stress-related failures.
Implementation Method 1
a stator is assembled to an inner peripheral wall of a cylindrical housing by an interference fitting process, such as, a shrink fitting process
Implementation Method 2
The curvature radii of the projecting and stopper portions are adjusted so as to prevent inhomogeneous stress on the motor housing
Data Source
AI summary
A stator assembly has a motor housing of a cylindrical shape and a stator fixed to an inner peripheral wall of the motor housing by a shrink fitting process. A stator core of the stator includes a projecting portion in contact with the motor housing and a stopper portion, which is smaller than the projecting portion in a radial direction. The stopper portion is in contact with the motor housing in an actual-use temperature range. The projecting portions and the stopper portions are alternately arranged in a circumferential direction in a cyclic manner. A cycle unit is composed of one or more than one projecting portion and one or more than one stopper portion. Multiple stator core sheets are built up in such a way that the cycle units are alternately arranged in an axial direction and neighboring stator core sheets are displaced in the circumferential direction by a predetermined shift angle. A curvature radius of the projecting portion at a position, at which the projecting portion is in contact with the motor housing, is smaller than a radius of a circumscribed circle of the projecting portion.