Flexible Gear Coupling Tooth Crowning for Larger Bogie Misalignment
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Solution Overview
Problem
The existing flexible gear couplings in railcar bogies face limitations in allowable relative displacement magnitude, particularly when vertical spring constants are reduced for improved ride quality, leading to excessive inclination displacement and hindering the addition of steering functions.
Innovation Solution
The design incorporates external gears with circular-arc shaped tooth tips and roots, where the tooth root crowning radius is smaller than the tooth tip crowning radius, and specific ratios of end tooth height to reference tooth height and tooth root to tooth tip crowning radii are set to increase the allowable inclination angle beyond the conventional 6°, allowing larger relative displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the vertical spring constant of the axle spring is reduced to improve ride quality, then ride quality is improved, but the vertical deflection of the axle spring increases causing the inclination displacement to exceed the allowable angle of the flexible gear coupling
Solution Approach 1:
The patent modifies the tooth geometry parameters of the flexible gear coupling, specifically implementing crowning on the tooth tips and roots with specific radius ratios. This changes the contact pattern and stress distribution, allowing the coupling to accommodate larger inclination angles (exceeding the conventional 6° limit) without compromising reliability, thereby resolving the contradiction between improved ride quality and maintained coupling reliability
2Adaptability or versatility
If a steering function is added to the bogie, then steering capability is improved, but the relative displacement between the traction motor rotation axis and pinion axis increases significantly exceeding the allowable relative displacement magnitude
Solution Approach 1:
The patent applies crowning to the tooth tips and roots with specifically optimized radius ratios, which transforms the gear contact characteristics. This allows the flexible gear coupling to handle the additional relative displacements caused by steering operations while maintaining reliable power transmission, enabling the integration of steering functions without exceeding displacement limits
3Reliability
If the tooth height at the ends is increased relative to the reference tooth height, then the allowable inclination angle increases, but the manufacturing complexity increases
Solution Approach 1:
The patent applies crowning - a curved surface modification - to the tooth tips and roots. This spherical/curved geometry approach naturally increases the allowable inclination angle while using established gear manufacturing techniques, balancing the need for improved performance with manufacturability constraints
Data Source
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AI summary
A flexible gear coupling includes two external gears and two internal gears meshing with the respective two external gears. A tooth root crowning radius of each external gear is smaller than a tooth tip crowning radius of the external gear. The external gear is formed such that a reference tooth height that is a tooth height at a tooth width direction middle position is smaller than an end tooth height that is a tooth height at a tooth width direction end position. A ratio of the end tooth height to the reference tooth height is set to 1.21 or more, and/or a ratio Rc/Rb of the tooth root crowning radius to the tooth tip crowning radius is set to 0.37 or less.