Planetary Gear Transmission Unit With Counterbalancing Helical Teeth
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Solution Overview
Problem
Existing planetary gear transmission units with helical teeth face challenges in withstanding high loads due to axial forces causing planet skewing, and existing solutions like flexpin shafts are complex and costly when combined with helical teeth.
Innovation Solution
A planetary gear transmission unit design featuring flexpin shafts with pairs of planet gears having opposite helical teeth angles, allowing for optimal load distribution and using conventional isotropic flexpin shafts and integrated double-row tapered or cylindrical roller bearings for improved stiffness and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If helical teeth are used to withstand high loads, then load capacity is improved, but axial forces cause planet skewing and gear instability
Solution Approach 1:
The patent employs asymmetric arrangement of helical planet gears where gears on opposite sides of the flexpin shaft have opposite helix directions. This asymmetric configuration causes axial forces to counterbalance each other, eliminating net axial thrust that would cause planet skewing, while maintaining the high load capacity benefits of helical teeth
Solution Approach 2:
The patent uses counterbalancing axial forces through oppositely directed helical gears to neutralize the axial thrust generated by helical tooth engagement. The axial force from one helical gear is counteracted by an equal and opposite axial force from the other helical gear, preventing planet gear skewing and maintaining stability under high loads
2Adaptability or versatility
If flexpin shafts are used to accommodate axial movements, then adaptability is improved, but planet skewing increases due to reduced stiffness
Solution Approach 1:
The asymmetric helical gear arrangement creates counterbalancing axial forces that eliminate the need for flexpin shafts to accommodate axial movements. This maintains the stiffness of rigid planet shafts, preventing planet skewing while still allowing the system to handle high loads effectively
3Strength
If larger radial bearing dimensions are used to withstand higher loads, then load capacity is improved, but gear rim thickness must be increased reducing compactness
Solution Approach 1:
The patent eliminates axial thrust forces through the counterbalancing helical gear arrangement before they can affect the planet bearings. This preliminary neutralization of axial forces allows the use of smaller radial bearing dimensions, maintaining compactness while still withstanding high radial loads effectively
Data Source
AI summary
A planetary gear transmission unit (10) includes a ring gear (17), a sun gear (18) and a planet carrier (19) driving a plurality of planet shafts (12) onto which planet gears (11) are rotatably mounted by way of planet bearings (13). The planet shafts are flexpin shafts (12) and each flexpin shaft (12) includes a pair of planet gears (11), each planet gear (11) of the pair being of the single helical type having a helix angle opposite to that of the other planet gear (11) of the pair. A gearbox (20) including a planetary gear transmission unit (10) according to embodiments of the invention and a wind turbine including such a gearbox (20) are also described.