Rotor Lamination Bore Recesses for High-Torque Shaft Coupling
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Solution Overview
Problem
Existing connections between the rotor shaft and rotor lamination stack in electric motors, particularly AC-powered ones, transmit limited torque and are prone to damage due to the shrinkage of crimping compounds used for insulation, further reducing torque transmission.
Innovation Solution
The rotor design features recesses in the bore of the rotor lamination that engage with projections on the rotor shaft, providing a strong connection and allowing high torque transmission, with asymmetrical recess slopes and a helical-like projection on the shaft for enhanced stability and insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a molding compound is applied between the rotor shaft and rotor lamination stack for electrical insulation, then electrical insulation is improved, but torque transmission is reduced due to shrinkage during hardening
Solution Approach 1:
The patent removes the molding compound entirely from the interface between the rotor shaft and rotor lamination stack. Instead, it uses a mechanical interference fit achieved through recesses in the rotor lamination that engage with protrusions on the rotor shaft, thereby eliminating the harmful shrinkage effect while maintaining electrical insulation through other means.
Solution Approach 2:
The patent introduces recesses with specific geometric profiles as an intermediary mechanical feature between the rotor shaft and rotor lamination stack. These recesses create a positive mechanical connection that transmits torque effectively without relying on molding compounds, thus mediating between the need for torque transmission and electrical insulation requirements.
2Ease of manufacture
If conventional connection methods are used between rotor shaft and rotor lamination stack, then assembly is simplified, but torque transmission capability is limited
Solution Approach 1:
The patent segments the connection interface by creating multiple recesses distributed around the rotor lamination stack. Each recess engages with a corresponding protrusion on the rotor shaft, distributing the torque transmission across multiple contact points. This segmented approach maintains assembly simplicity while significantly enhancing torque transmission capability.
Solution Approach 2:
The recesses are designed with asymmetric profiles having different slope angles on opposite sides. This asymmetry creates optimized engagement characteristics for torque transmission in both rotational directions, allowing the connection to adapt to bidirectional torque loads while maintaining straightforward assembly procedures.
3Power
If high torque is transmitted through conventional connections, then power output is improved, but damage to rotor lamination occurs
Solution Approach 1:
The patent designs recesses with rounded bottom corners and controlled slope angles to prevent stress concentration before high torque is applied. The geometric profile of the recesses is optimized in advance to distribute stresses evenly during torque transmission, cushioning against potential damage to the rotor lamination while enabling high power output.
Solution Approach 2:
The patent changes the geometric parameters of the connection interface by specifying precise slope angles (10-45 degrees) and rounded corner radii (0.1-2 mm) for the recesses. These parameter optimizations enable the rotor lamination to withstand high torque loads by distributing mechanical stresses uniformly, thereby maintaining rotor integrity at high power levels.
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a rotor lamination (7) for a rotor (3) of a permanent magnet AC electric motor (1), with a bore (8) for receiving a rotor shaft (4). The bore (8) has several recesses (16) around its circumference. The recesses (16) are shaped like humps and have a radius (18) at their point furthest from the center of the bore (8). The transitions from the radius (18) to the circumference of the bore (8) have different slopes on both sides of the recesses (16).