Electric Rotating Machine Rotor Shaft Insertion Stress Reduction
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Solution Overview
Problem
The existing electric rotating machines face challenges in achieving high insertion accuracy and reducing stress during the pressure-insertion of a shaft into a rotor core due to the hardness difference between the shaft and the rotor core, leading to potential chipping and significant radial stress.
Innovation Solution
The design incorporates a rotor with radially projecting portions, extension portions, and plate-shaped bridge portions that connect these features, allowing for effective distribution of compression stress and reducing radial stress during shaft insertion, while also enhancing resistance to centrifugal force through strategically placed hollow portions and V-shaped magnet arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the shaft is pressure-inserted into the center hole of the core made of high-hardness electromagnetic steel sheets, then the rotor structure is simplified and assembly is easier, but the shaft cannot achieve sufficiently high insertion accuracy and chips occur during insertion due to the hardness difference
Solution Approach 1:
The invention changes the surface geometry parameter of the shaft by forming convex lines through knurling on the outer peripheral surface of the shaft's fitting portion. This surface modification creates a textured interface that allows the softer shaft to engage with the harder core while maintaining insertion accuracy and preventing chipping, effectively resolving the contradiction between ease of assembly and manufacturing precision.
2Ease of manufacture
If the shaft is pressure-inserted into the center hole of the core, then the rotor structure is simplified, but a large stress occurs in the radial direction due to the hardness difference between the shaft and core
Solution Approach 1:
The knurling process changes the surface parameters of the shaft, creating convex lines that distribute the contact area during pressure insertion. This surface modification reduces the concentration of radial stress by spreading the insertion force across multiple contact points, thereby reducing overall radial stress while maintaining the simplified rotor structure.
3Manufacturing precision
If convex lines are formed by knurling on the shaft surface to improve insertion accuracy, then insertion accuracy and circumferential stress resistance improve, but a large stress still occurs in the radial direction
Solution Approach 1:
The knurling process modifies the surface geometry parameter of the shaft by creating periodic convex lines. This surface parameter change increases the effective contact area during insertion, distributing radial stress across multiple engagement points between the shaft convex lines and the core's engaging portions, thereby reducing peak radial stress while maintaining high insertion accuracy.
Data Source
AI summary
The electric rotating machine includes a stator having an inner hole, a rotor disposed in the inner hole of the stator with a gap with an inner periphery of the stator and formed with magnet housing holes each housing a permanent magnet as a magnetic pole embedded in the outer periphery of the rotor, and a shaft pressure-inserted into a center hole of the rotor. The rotor includes, for each adjacent two of the magnet housing holes, a beam portion formed radially outside the magnet housing holes, a projecting portion projecting radially inward to define the center hole, an extension portion formed radially outside the projecting portion and radially outside the magnet holes, and a plate-shaped bridge portion connecting the beam portion and the extension portion.