Coaxial Torque-Splitting Gear Assembly With Centered Nested Shafts
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Solution Overview
Problem
Existing transmission devices for splitting torque between two coaxial gears in planetary gearing for aeronautic applications face challenges in manufacturing and assembly complexity, leading to errors in load distribution and alignment precision.
Innovation Solution
A transmission device comprising two coaxial transmission shafts with radial clearance, where sun gears are formed integrally on the shafts and flanges are axially supported to split torque evenly, using welding or mechanical couplings for assembly, and employing centring rings for precise alignment and reduced assembly tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two hollow transmission shafts are used with radial clearance to split torque between two sun gears, then torque distribution is achieved, but manufacturing and assembly complexity increases
Solution Approach 1:
The transmission shaft is divided into two separate hollow shafts that can be manufactured and assembled independently. Each shaft carries one sun gear, allowing separate manufacturing processes and simplifying the overall assembly. The radial clearance between the shafts enables independent positioning and assembly without requiring complex precision machining of a single integrated structure.
Solution Approach 2:
One hollow transmission shaft is positioned inside the other hollow shaft, creating a nested configuration. This nesting arrangement allows both shafts to be housed within a compact space, reducing the overall device footprint while maintaining the torque splitting function. The inner shaft can be assembled separately and then inserted into the outer shaft, simplifying the manufacturing process.
2Productivity
If flanges are axially supported to split torque evenly, then torque splitting efficiency improves, but assembly precision requirements increase
Solution Approach 1:
Centring rings are introduced as intermediary elements between the two hollow transmission shafts. These rings provide a mechanical means to maintain precise axial alignment and centring of the shafts during assembly and operation. The centring rings eliminate the need for extremely tight manufacturing tolerances on the shafts themselves, as the alignment function is transferred to the centring rings which can be manufactured with standard tolerances.
3Ease of manufacture
If welding or mechanical couplings are used to assemble shafts, then assembly simplicity improves, but alignment precision may decrease
Solution Approach 1:
The centring rings are pre-installed on the transmission shafts before the final welding or mechanical coupling assembly. This preliminary action establishes the correct axial alignment and centring of the shafts in advance. By setting the alignment position before permanent joining, the subsequent welding or coupling operations can be performed with simpler fixtures and less precision requirement, while the final aligned position is maintained by the previously installed centring rings.
Data Source
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AI summary
A transmission device (34) for splitting torque between two coaxial gears (14,15), in particular for a planetary gearing (1) for aeronautic applications, has a motion input member (3) and two transmission members (36,37), which are coaxial and have respective shafts provided with gears at an axial end and respective external flanges, at the opposite axial end; the two flanges are axially facing and placed abutting against each other, and are fixed to the motion input member (3) so as to split the torque transmitted from the motion input member (3) between the two flanges; one of the two shafts (39) is axially hollow and houses, with radial clearance, an intermediate portion of the other shaft (38); the latter is formed by at least two pieces (58,59) which are coaxial and fixed to each other.