External Rotor Lamination Hub Connection for Reliable Torque Transfer
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Solution Overview
Problem
Existing rotors for external rotor motors face challenges in cost-effectively connecting a stack of laminated sheets to a carrier while ensuring reliable torque transmission.
Innovation Solution
The rotor connects the stack of laminated sheets to the carrier using a shaft-hub connection, where the sheets are made of ferromagnetic steel and welded together, with protrusions on the outside for secure engagement with the carrier's slots, minimizing material impairment and enhancing stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the stack of laminated sheets is connected to the carrier using traditional connection methods, then reliable torque transmission is achieved, but manufacturing cost increases and assembly complexity increases
Solution Approach 1:
The patent replaces traditional mechanical connection methods (such as screws, rivets, or complex mechanical fasteners) with a shaft-hub connection system where protrusions on the laminated sheets engage directly with slots in the carrier. This substitution simplifies the connection mechanism, reduces manufacturing cost, and eliminates the need for additional fastening components while maintaining reliable torque transmission through the interlocking geometry of the shaft-hub connection.
Solution Approach 2:
The connection system is segmented into discrete protrusions on the laminated sheets and corresponding slots in the carrier. This segmentation allows for modular assembly, simplifies manufacturing of individual components, and enables the connection to be achieved through simple engagement of these segmented elements rather than requiring a complex unified connection structure.
2Stability of the object's composition
If weld seams are added to connect laminated sheets, then structural stability improves, but magnetic properties of the steel sheets are impaired
Solution Approach 1:
The patent extracts the connection function from the magnetic steel sheets themselves by adding non-magnetic protrusions that extend from the sheet stack. These protrusions are taken out as separate structural elements that provide mechanical stability and connection capability without requiring weld seams that would impair the magnetic properties of the steel sheets. The protrusions can be made from non-magnetic materials or positioned such that they minimize magnetic interference.
Solution Approach 2:
The patent applies local quality by providing protrusions only at specific locations on the laminated sheets where connection to the carrier is needed, rather than welding throughout the entire structure. This localized approach provides structural stability at the connection points while leaving the bulk of the magnetic steel sheets unwelded and thus preserving their magnetic properties in the majority of the rotor structure.
3Stability of the object's composition
If the carrier surrounds the entire stack of laminated sheets, then mechanical stability is improved, but rotor mass increases and efficiency decreases
Solution Approach 1:
The patent applies partial action by having the carrier surround only a portion of the laminated sheet stack rather than the entire stack. The shaft-hub connection with protrusions and slots provides sufficient mechanical stability for torque transmission over this partial coverage area, eliminating the need for the carrier to extend along the full axial length of the stack. This partial coverage significantly reduces rotor mass while maintaining adequate mechanical stability through the localized connection points.
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 solution enables cost-effective and reliable torque transmission from the laminated sheet stack to the carrier, reducing material costs and improving motor efficiency by optimizing the mass distribution and mechanical stability of the rotor.
Implementation Method 1
The metal sheets forming the stack of the short-circuit ring are welded together
Data Source
AI summary
A rotor for an external rotor motor is described, having a stack of ferromagnetic steel sheets, permanent magnets which are fastened to an inner side of the stack, and a carrier which has a hub for a shaft and is fastened to the stack. It is provided that the carrier is connected to the stack by a shaft-hub connection.