Coupled Planetary Gearbox With Overlapping Speed Ratios
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Solution Overview
Problem
Modern aircraft engines face challenges in meeting increasing electric power demands due to the limited power extraction potential of high pressure spools, necessitating an efficient transmission system to manage varying speed ratios between the low pressure spool and aircraft accessories.
Innovation Solution
A coupled planetary gearbox transmission system with multiple epicyclical gear sets and clutches is employed, allowing for shifting between various transmission speeds by controlling the engagement of clutches to achieve overlapping speed ranges and optimal output/input speed ratios, thereby efficiently transferring power from the low pressure spool to aircraft accessories.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-stage planetary gearbox is used, then the structure is simple, but it cannot provide multiple overlapping speed ratios needed for efficient power extraction
Solution Approach 1:
The transmission system is divided into two separate planetary gear sets (first and second planetary gear sets), each capable of providing different speed ratios. This segmentation allows the system to achieve multiple overlapping speed ratios by selectively engaging different gear sets through the clutch mechanism, resolving the contradiction between versatility and structural simplicity.
Solution Approach 2:
The system employs a dynamic clutch mechanism that can selectively engage or disengage between the two planetary gear sets based on operating conditions. This dynamic switching capability enables the transmission to adaptively provide different speed ratios, achieving versatility while maintaining a relatively simple base structure that only becomes complex when the dynamic switching is implemented.
2Use of energy by moving object
If the transmission converts a wide input speed range to a narrow output speed range, then power efficiency is improved, but brake wear increases due to frequent shifting
Solution Approach 1:
The system pre-establishes multiple overlapping speed ratios through the two planetary gear sets before shifting is needed. The clutch mechanism is designed to smoothly transition between these pre-configured ratios, allowing the transmission to maintain optimal efficiency across a wide input speed range without requiring frequent aggressive braking and shifting operations, thus reducing brake wear while preserving power efficiency.
3Reliability
If traditional non-overlapping speed ratios are used, then the transmission structure is simpler, but doorbelling occurs at shift points reducing reliability
Solution Approach 1:
The patent merges the output speed ranges of two planetary gear sets to create overlapping speed ratios. This merging of speed ranges ensures continuous smooth transition between gear sets, eliminating doorbelling effects at shift points. The overlapping configuration, while more complex than non-overlapping ratios, provides the reliability benefit of smooth shifting by ensuring that there is always an engaged gear set during transitions.
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
The system effectively converts a wide input speed range into a narrower output speed range, enhancing power efficiency and reducing brake wear, while preventing 'doorbelling' at shift points by providing overlapping speed ranges, thus addressing the power demand and efficiency requirements of modern aircraft engines.
Implementation Method 1
a first epicyclical gear set that includes a first ring gear coupled to the input shaft, a first sun gear, a first planetary gear set, and a first planetary carrier connected to the first planetary gear set
Data Source
AI summary
Disclosed is a transmission, including: an input shaft; an output shaft; a gear system connected between the input shaft and the output shaft, the gear system including: a first epicyclical gear set that includes a first ring gear coupled to the input shaft, a first sun gear, a first planetary gear set, and a first planetary carrier connected to the first planetary gear set; and a second epicyclical gear set that includes a second ring gear, a second sun gear, a second planetary gear set, and a second planetary carrier connected to the second planetary gear set, wherein: the input shaft is coupled to the first ring gear and the second planetary carrier; and the first planetary carrier is coupled to the second ring gear; and clutches that engage the first epicyclical gear set and the second epicyclical gear set, the clutches shifting the transmission to generate overlapping transmission speeds.