Rotary Electric Machine Frame with Variable Inner Diameter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional rotary electric machines with split cores face issues of vibration noise due to out-of-plane deformation caused by the barrel-like shape of the core after coil winding, particularly at the end portions, where the fastening force is insufficient, leading to inadequate out-of-plane rigidity and increased core loss.
Innovation Solution
The rotary electric machine features a frame with a smaller inner diameter at both end portions compared to the axial middle portion, enhancing the fitting fastening force at the ends, which counteracts the barrel-like shape bulge and maintains sufficient contact pressure, thereby reducing out-of-plane deformation and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a large interference is applied to increase fastening force at end portions, then out-of-plane rigidity is improved, but core loss and core deformation increase due to local excessive fastening
Solution Approach 1:
The frame is designed with different inner diameters at different axial positions: the end portions have smaller inner diameters than the axial middle portion. This creates locally different interference fits: larger interference at end portions to increase fastening force and out-of-plane rigidity, and smaller interference at the middle portion to avoid excessive fastening. This local variation in geometry resolves the contradiction by applying appropriate fastening force only where needed.
2Ease of manufacture
If uniform interference is applied across the frame, then manufacturing is simplified, but out-of-plane deformation occurs due to insufficient fastening force at end portions
Solution Approach 1:
The frame incorporates local geometric variations with smaller inner diameters at end portions and a larger inner diameter at the axial middle portion. This design provides locally enhanced fastening force at the end portions to prevent out-of-plane deformation, while maintaining relatively simple overall manufacturing processes. The local quality principle allows the frame to address deformation issues without requiring complex uniform reinforcement throughout.
3Strength
If the frame rigidity is increased at end portions, then out-of-plane rigidity is improved, but dimensional constraints are violated
Solution Approach 1:
The frame design uses local geometric variation where only the end portions have smaller inner diameters, while the axial middle portion maintains a larger inner diameter. This localized approach increases out-of-plane rigidity at the end portions without requiring a reduction in the overall frame dimensions, thereby satisfying dimensional constraints while improving structural rigidity where needed.
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 configuration effectively suppresses vibration noise and out-of-plane deformation by increasing the fitting fastening force at the end portions, ensuring a stable and quiet operation even with concentrated winding split cores.
Implementation Method 1
an inner diameter of each of both end portions is smaller than an inner diameter of an axial middle portion, and a fitting fastening force between the frame and each split core is set to be greater at both the end portions than at the axial middle portion
Data Source
AI summary
Provided is a rotary electric machine that is able to suppress vibration noise of the rotary electric machine caused by an out-of-plane deformation. The rotary electric machine includes a stator including a frame being an annular member, and a plurality of split cores arranged in an annular shape and fitted to and held by a radially inner portion of the frame, wherein the frame is formed such that an inner diameter of each of both end portions thereof is smaller than an inner diameter of an axial middle portion thereof, and fitting fastening force between the frame and each split core is set to be greater at both the end portions than at the axial middle portion.