Railcar Flexible Gear Coupling Crowning for Higher Inclination
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Solution Overview
Problem
The existing flexible gear couplings in railcar bogies face limitations in allowable relative displacement magnitude, which restricts the addition of steering function due to excessive inclination displacement beyond the allowable angle, especially when vertical spring constant is reduced for improved ride quality.
Innovation Solution
The railcar flexible gear coupling design features 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 a ratio of end tooth height to reference tooth height is set to 1.21 or more, or a ratio of tooth root crowning radius to tooth tip crowning radius is set to 0.37 or less, allowing increased allowable inclination angle.
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 the 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 invention changes the geometric parameters of the gear teeth by introducing crowning radii at the tooth tips and roots. Specifically, a tooth tip crowning radius Rb and a tooth root crowning radius Rc are formed, where Rc < Rb. This parameter change allows the gear coupling to accommodate larger inclination angles (exceeding the conventional 6° limit) while maintaining proper meshing contact, thus resolving the contradiction between improved ride quality and maintained reliability.
2Adaptability or versatility
If a steering function is added to the parallel cardan driving bogie, then the steering capability is improved, but the relative displacement between the traction motor rotation axis and pinion axis increases causing the inclination displacement to significantly exceed the allowable relative displacement magnitude
Solution Approach 1:
The invention modifies the gear tooth geometry by forming circular-arc shaped crowning at both tooth tips and roots with different radii (Rc < Rb). This geometric parameter change enables the flexible gear coupling to handle the additional relative displacement caused by steering operations while maintaining acceptable meshing conditions, thus enabling steering functionality without exceeding displacement limits.
Solution Approach 2:
The invention introduces curved surfaces (crowning) at the gear tooth tips and roots. The tooth tip crowning radius Rb and tooth root crowning radius Rc create spherical-like contact zones that accommodate angular misalignment and relative displacement during steering. This curvature application allows the gear coupling to maintain contact under inclined conditions beyond the conventional 6° limit.
3Ease of manufacture
If the conventional flexible gear coupling design is used, then the manufacturing is simple, but the allowable relative displacement magnitude is limited to about 6° inclination angle
Solution Approach 1:
The invention changes the tooth geometry parameters by adding crowning radii Rb and Rc to the conventional gear design. While this adds some manufacturing complexity compared to standard gears, the crowning can be formed using conventional gear finishing processes. The parameter change enables the coupling to accommodate inclination angles exceeding 6°, thus improving adaptability while maintaining reasonable manufacturability.
Data Source
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.