Self-Scavenging Gear Shield for Rotary Wing Gearbox Lubricant Management
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Solution Overview
Problem
In rotary wing aircraft gearboxes, excess lubricant can lead to increased friction and temperature, causing power loss due to inadequate lubricant circulation, resulting in lubricant churning events.
Innovation Solution
A gearbox design featuring a shield assembly around the gears that utilizes the rotational motion to create a pumping action, routing excess lubricant away from the gear through a shield gap and flow channel, ensuring continuous circulation and reducing friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lubricant is circulated through the system quickly, then friction and temperature are reduced, but lubricant circulation speed is insufficient in some operating conditions
Solution Approach 1:
The gear itself performs the lubrication function by scavenging lubricant through its rotation. The gear teeth interact with the lubricant in the sump, creating a pumping action that draws lubricant through the meshing points without requiring an external pump system. This self-service approach ensures lubricant circulation is directly coupled to gear operation, eliminating the lag between gear rotation and lubricant delivery.
Solution Approach 2:
The invention extracts the lubrication function from a separate circulation system and integrates it directly into the gear mechanism. By removing the dependency on external pump systems and lubricant delivery mechanisms, the gear assembly becomes self-lubricating through its own rotational motion, directly addressing the insufficiency of external circulation systems.
2Reliability
If lubricant levels around the gears rise above a selected level, then lubrication is improved, but friction increases and power output decreases
Solution Approach 1:
The invention creates different lubricant levels in different locations: a deeper lubricant level at the gear periphery for adequate lubrication, and a lower lubricant level at the gear meshing points to reduce friction. The shield structure confines lubricant to specific zones, allowing the gear teeth to operate in a lubricant-depleted zone while the gear body rotates through a lubricant-rich zone for periodic replenishment.
Solution Approach 2:
The shield divides the lubricant space into distinct regions: an inner region close to the gear where lubricant is scavenged away to reduce friction, and an outer region where lubricant accumulates for periodic replenishment. This segmentation allows simultaneous optimization of both lubrication (in the outer region) and friction reduction (in the inner region).
3Reliability
If excess lubricant is in contact with the gears, then lubrication is maintained, but lubricant churning events occur causing rapid temperature rise and power loss
Solution Approach 1:
The shield acts as an intermediary structure between the gear and the lubricant sump. It controls the interaction by allowing the gear to periodically contact lubricant while preventing continuous submersion. The shield creates a buffer zone that mediates between the need for lubrication and the need to avoid churning, enabling controlled lubricant uptake without excessive contact.
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 solution effectively maintains power output by reducing friction and preventing uncontrolled temperature rises by efficiently managing lubricant levels around the gears.
Implementation Method 1
Rotating gears that are utilized to transmit power and/or rotational speed, such as those in a gearbox of a rotary wing aircraft like helicopters, are typically lubricated and/or cooled by a lubricant.
Data Source
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AI summary
A gearbox assembly includes a gearbox housing and a gear located in the housing and rotatable about a central axis. One or more gear shields are fixed in the housing and at least partially surround the gear. The one or more gear shields define a cavity between the gear and the one or more gear shields. The one or more gear shields are configured such that a pumping action is created by the gear rotation to direct gearbox lubricant out of the cavity. A method of scavenging lubricant from a gearbox includes pumping a flow of lubricant circumferentially around a cavity defined between a gear and a gear shield at least partially surrounding the gear via rotation of the gear about a central axis. The flow of lubricant is urged from the cavity into a lubricant outlet. The lubricant is urged through a lubricant channel in an axial direction.