Electric Motor Rotor Coupling for High-Speed Alignment Stability
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Solution Overview
Problem
Existing mechanical couplings between the crankshaft and steel plates in high-performance electric motors fail to maintain precise alignment and continuous contact under high rotational speeds, torques, and thermal stresses, leading to angular misalignment and inefficient operation.
Innovation Solution
A rotor design featuring a shape coupling mechanism with isosceles trapezoidal radial seats and 'V'-shaped teeth on the crankshaft and steel plates, allowing interference fit assembly and self-centering, ensuring precise alignment and reduced mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a press-fit coupling is used between the crankshaft and steel plate stacks, then angular misalignment is prevented at low rotation speeds, but significant angular misalignment occurs at high rotation speeds and high torques
Solution Approach 1:
The coupling interface is segmented into multiple radial seats on the crankshaft that engage with corresponding features on the steel plate stacks. This segmentation distributes the torque transmission across multiple contact points, preventing the angular misalignment that occurs with a single press-fit coupling at high speeds and torques.
2Ease of manufacture
If a press-fit coupling is used between the crankshaft and steel plate stacks, then assembly is simple, but the coupling fails under thermal stresses and torque reversals
Solution Approach 1:
The coupling mechanism incorporates dynamic elements that allow for thermal expansion and contraction while maintaining engagement. The radial seats and corresponding features are designed to maintain contact under varying thermal conditions and torque directions, ensuring reliable coupling performance throughout the operating range.
3Power
If shape couplings are used between the steel plate stacks and rotor, then some torque transmission is achieved, but adequate performance is not ensured under combined high speeds, torques, and thermal stresses
Solution Approach 1:
The coupling system utilizes composite structural elements combining the crankshaft material with the steel plate stack material, each optimized for their specific functions. The radial seats in the crankshaft and corresponding engagement features on the steel plates create a composite coupling system that handles torque transmission while accommodating the different thermal and mechanical properties of the two materials.
Data Source
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AI summary
A rotor (4) for an electric motor comprising a crankshaft (8) extending along a prevailing extension axis (X-X) coinciding with an axis of rotation of the crankshaft (8), at least one steel plate (12) provided with slots (16) for housing magnets, the steel plate (12) being provided with a central seat (20), keyed to an outer side wall (24) of the crankshaft (8) according to an interference coupling, wherein the steel plate (12) is coupled to the crankshaft (8) at said central seat (20) by means of a first tooth (36) obtained on the steel plate (12), which projects towards the associated crankshaft (8) and a first radial seat (40), obtained on said outer side wall (24) of the crankshaft (8). The first radial seat (40) has an isosceles trapezium cross-section delimited laterally by a pair of oblique sides (44) converging towards the axis of rotation; the first tooth (36) has a 'V' cross-section with a pair of curvilinear side walls (48), suitable for interfacing against said oblique sides (44) of the first radial seat (40) .