Hydroformed Rotor Shaft Geometry for Bearing Accuracy
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Solution Overview
Problem
The existing rotor manufacturing method decreases the dimensional accuracy of the portion of the rotary shaft around which the bearing member is to be placed due to hydroforming, leading to potential misalignment and reduced precision, and increasing the size of the rotor manufacturing apparatus to prevent this issue is not feasible.
Innovation Solution
A rotor manufacturing method where the shaft has a cylindrical shape with a larger inside diameter for the portion fixed to the rotor core, allowing for greater circumferential stress and less deformation in the portion around the bearing member, preventing dimensional accuracy loss without enlarging the apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydroforming process is performed to fix the rotary shaft to the laminated core, then the rotary shaft is expanded and fixed to the laminated core, but the dimensional accuracy of the portion of the rotary shaft around which the bearing member is to be placed decreases
Solution Approach 1:
The rotary shaft is divided into multiple portions along its axial direction, with each portion having different inside diameters. The first portion (for bearing placement) has a smaller inside diameter to maintain dimensional accuracy, while the second portion (for fixing to laminated core) has a larger inside diameter to allow expansion during hydroforming. This segmentation allows different functional requirements to be satisfied in different regions of the same component.
Solution Approach 2:
Different portions of the rotary shaft are given different local properties - specifically, different inside diameters tailored to their specific functions. The bearing portion maintains small inside diameter for precision, while the fixing portion has large inside diameter for deformability. This local differentiation resolves the contradiction between needing precision in one area and deformability in another.
2Manufacturing precision
If the radial thickness of the rotary shaft is increased to enhance rigidity and prevent deformation, then the dimensional accuracy of the bearing portion is maintained, but the hydroformer-produced pressure must be increased and the hydroformer size increases
Solution Approach 1:
Instead of uniformly increasing the radial thickness of the entire rotary shaft, the invention segments the shaft into portions with different inside diameters. This allows the bearing portion to maintain its precision without requiring increased thickness, while the fixing portion has sufficient thickness for hydroforming. Consequently, the hydroformer can operate at normal pressure levels without requiring size increases.
Solution Approach 2:
The rotary shaft exhibits local quality variations in terms of inside diameter across different axial portions. The bearing portion has small inside diameter for precision without needing increased thickness, while the fixing portion has larger inside diameter for deformability. This local differentiation eliminates the need to increase overall radial thickness, thereby avoiding the need for a larger hydroformer apparatus.
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 method effectively maintains the dimensional accuracy of the shaft portion around the bearing member while preventing deformation, ensuring precise rotor assembly and operation without increasing the apparatus size.
Implementation Method 1
fixing the shaft to the rotor core by a hydroforming process that involves filling an internal space of the shaft with a fluid and expanding the shaft with an internal pressure produced by the fluid
Implementation Method 2
the portion of the rotary shaft facing the laminated core is expanded (or plastically deformed) and thus fixed to the laminated core
Implementation Method 3
expanding the shaft with an internal pressure produced by the fluid
Data Source
AI summary
The rotor manufacturing method includes the step of fixing a shaft to a rotor core by hydroforming. The shaft has a cylindrical shape in which an inside diameter of a first portion of the shaft to be placed on an inner peripheral surface of a shaft insertion hole is larger than an inside diameter of a second portion of the shaft located on one side in a rotation axis direction relative to the first portion.