Pass-Through Coupling Shaft for Compact Misalignment-Tolerant Drives
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Solution Overview
Problem
Conventional rotorcraft main rotor gearboxes require longer drive systems due to the need for axial space in coupling shafts to accommodate misalignment, leading to undesirable longitudinal lengths and placement of heavy components away from the aircraft's center of gravity.
Innovation Solution
The implementation of a pass-through coupling shaft that receives through the interior of the intermediate gearbox, allowing for longitudinal overlap and reducing packaging length by integrating couplings and using annular seals and anti-flail features for secure connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional coupling shafts are used to isolate motions between the main rotor gearbox and intermediate gearbox, then misalignment is accommodated, but the axial space required increases the longitudinal length of the drive system
Solution Approach 1:
The coupling shaft is passed through the intermediate gearbox, nesting the coupling function within the gearbox structure. This eliminates the need for separate axial space for the coupling shaft, as it now occupies space within the intermediate gearbox's existing envelope, thereby reducing the overall longitudinal length while maintaining misalignment accommodation capability
Solution Approach 2:
The coupling shaft and intermediate gearbox are merged into a single integrated structure where the coupling shaft passes through the gearbox. This combines the function of motion isolation and misalignment accommodation with the gearbox structure, eliminating the need for additional axial space and reducing the overall drive system length
2Reliability
If the drive system is lengthened to accommodate conventional coupling shafts, then misalignment is isolated, but heavy components must be placed further from the aircraft's center of gravity
Solution Approach 1:
By nesting the coupling shaft within the intermediate gearbox, the overall drive system length is reduced, allowing heavy components to be positioned closer to the aircraft's center of gravity. This maintains the motion isolation function while improving the weight distribution and flight dynamics
3Length of moving object
If the coupling shaft passes through the intermediate gearbox, then longitudinal overlap is achieved and packaging length is reduced, but sealing and connection complexity increases
Solution Approach 1:
Annular seals are installed at the interfaces where the coupling shaft passes through the intermediate gearbox. These thin film seals provide effective sealing against lubricant leakage while adding minimal structural complexity, enabling the pass-through configuration to achieve reduced packaging length
4Reliability
If couplings are integrated onto the coupling shaft, then connection security is improved, but manufacturing and assembly complexity increases
Solution Approach 1:
The couplings are integrated directly onto the coupling shaft, merging the connection function with the shaft structure. This integration improves connection security and reliability by eliminating separate coupling components, while the modular design allows for standardized manufacturing and assembly processes
Data Source
AI summary
A drive system has a gearbox, comprising a passage therethrough, a coupling shaft disposed at least partially within the passage and a first coupling carried by a first end of the coupling shaft. The first coupling is configured to accommodate misalignment. The drive system also has a second coupling carried by a second end of the coupling shaft. The second coupling is also configured to accommodate misalignment.