Permanent Magnet Rotor Interference Fit Retention
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Solution Overview
Problem
High-speed rotating components in electrical machines, such as permanent magnets, tend to migrate from their intended positions due to inertial forces, leading to potential failure at high rotational speeds, as existing retention methods like adhesives and mechanical clamping are insufficient.
Innovation Solution
A permanent magnet rotor design that incorporates a rotor core with deformed material to bias permanent magnets radially outward against a fixation sleeve, utilizing pressure tools to create an interference fit and additional mechanisms like shrink fitting with a carbon fiber sleeve to maintain contact pressure, ensuring the magnets remain securely positioned.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If adhesive retention techniques are used for permanent magnets, then the structure is simple, but the rotor fails at high rotational speeds due to insufficient retention force
Solution Approach 1:
The patent replaces adhesive retention with a mechanical interference fit system. Pressure tools with radially outwardly directed protrusions are pressed into the rotor core, deforming the material to create an interference fit that mechanically retains the permanent magnets against the rotor core, eliminating the need for adhesives and providing reliable retention at high speeds.
Solution Approach 2:
The patent changes the physical state of the rotor core material through plastic deformation. By applying radial pressure through the pressure tools, the material transitions from its original state to a deformed state with increased density and residual compressive stresses, creating the interference fit necessary for high-speed magnet retention.
2Reliability
If mechanical clamping components are used for high-speed applications, then magnet retention is improved, but the device complexity increases
Solution Approach 1:
The patent merges the functions of clamping and retention into a single integrated system. The pressure tools serve dual purposes: they deform the rotor core material to create the interference fit while simultaneously providing the clamping force to retain the magnets. This eliminates the need for separate clamping components and retention structures.
Solution Approach 2:
The rotor core material serves its own retention function through self-deformation. When the pressure tools press into the rotor core, the material deforms plastically and creates residual compressive stresses that automatically retain the magnets. The system uses the rotor core's own material properties to provide retention, eliminating the need for additional retention components.
3Reliability
If rotor core material is deformed to create interference fit, then magnet retention at high speed is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs the material deformation action during the assembly process itself. The pressure tools are inserted into pre-formed cavities in the rotor core, and the radial pressing action that deforms the material is performed as part of the magnet assembly operation. This preliminary deformation action prepares the interference fit before the magnets are fully installed, simplifying the overall manufacturing process.
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 extends the speed range of the rotor by preventing air gaps between magnets and the rotor core, enhancing structural integrity and preventing catastrophic failure at high rotational speeds.
Implementation Method 1
deforming material of a rotor core so as to bias permanent magnets positioned upon the rotor core against a fixation sleeve
Implementation Method 2
deforming material of a rotor core will create residual compressive stresses in the deformed material
Implementation Method 3
some elastic recovery of the deformed material may occur, however, sufficient contact pressure will be maintained
Data Source
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AI summary
A method of making a permanent magnet rotor includes interference fitting pressure tools into bores in a rotor core as to deform material of the rotor core outwardly to bias permanent magnets mounted thereon in a radially outward direction against a fixation sleeve.