Gearbox Shield Prevents Lubricant Submersion in Extreme Attitudes
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Solution Overview
Problem
Aircraft gearboxes for high attitude applications face challenges in preventing gears and bearings from becoming submerged in lubricant during extreme orientations, leading to increased wear and reduced power output.
Innovation Solution
The gearbox design includes a shield that surrounds a portion of the gear to prevent lubricant submersion, with a chamber that maintains lubrication levels and utilizes centrifugal forces and windage to circulate lubricant effectively, ensuring continuous lubrication without submerging the gear and its bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large lubricant reservoirs are used to prevent submersion of gears and bearings in extreme attitudes, then the risk of submersion is reduced, but the device complexity and size increase
Solution Approach 1:
The patent divides the lubricant reservoir into two distinct chambers: a main reservoir and a shielded chamber. The shielded chamber is isolated from the main reservoir and contains the gear and bearing assemblies. This segmentation allows the gear assembly to be protected from submersion while the main reservoir can be optimized for lubricant storage capacity, resolving the contradiction between preventing submersion and maintaining compact size.
Solution Approach 2:
A shield structure acts as an intermediary barrier between the lubricant in the main reservoir and the gear/bearing assemblies. The shield includes openings that allow lubricant to pass through for lubrication while preventing direct submersion of the rotating components. This intermediary structure enables selective protection while maintaining the necessary lubrication function.
2Reliability
If gears and bearings are kept out of lubricant to prevent submersion, then wear is reduced, but continuous lubrication becomes difficult to maintain
Solution Approach 1:
The shield structure incorporates openings and pathways that dynamically allow lubricant to flow through to the gear and bearing assemblies during operation. The design enables lubricant to reach the components that need protection from submersion, maintaining continuous lubrication while preventing harmful submersion. This dynamic approach resolves the contradiction between wear prevention and lubrication maintenance.
3Reliability
If remote lubricant reservoirs with pumps are used to prevent submersion, then gear submersion is avoided, but the device complexity and power requirements increase
Solution Approach 1:
The patent extracts the gear and bearing assemblies from the main lubricant reservoir environment by placing them in a separate shielded chamber. This extraction eliminates the need for complex pump systems and remote reservoirs, as the lubrication can be achieved through passive flow through the shield openings. The harmful element (direct submersion) is removed while maintaining the beneficial element (lubrication).
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively prevents gear and bearing submersion, reduces wear, maintains power output, and allows for a more compact gearbox configuration by ensuring consistent lubrication, even in extreme orientations.
Implementation Method 1
utilizes centrifugal forces and windage to circulate lubricant effectively
Implementation Method 2
utilizes centrifugal forces and windage to circulate lubricant effectively
Data Source
AI summary
A gearbox for an auxiliary power unit (APU) includes features that prevent submersion of gears in lubricant in extreme attitude orientations. The gearbox includes a plurality of gears that drive various pumps, generators and/or other aircraft systems. A shield surrounds a portion of one of the plurality of gears to prevent lubricant from submerging the gear. The shield defines at least a portion of an open chamber that is at least partially surrounded by lubricant at extreme attitude orientations.