Planetary Gearbox With Dual Ring Gears for Turbine Speed Reduction
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Solution Overview
Problem
Aircraft gas turbine engines require a reduction gearbox to match the high rotational speed of turbines with propellers, which adds weight and complexity, indicating a need for a more efficient speed reduction mechanism.
Innovation Solution
A planetary gearbox with a sun gear, planet gear assemblies, and ring gears is used, where the planet carrier and one of the ring gears are configured to be operatively connected to an input or output, and the rotation of the remaining ring gear is limited, allowing for efficient speed reduction and torque increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional reduction gearbox is used to reduce turbine rotational speed to propeller speed, then the speed reduction function is achieved, but the weight and complexity of the engine increase
Solution Approach 1:
The planet gear assembly is segmented into multiple independent planet gears (typically three) that rotate on individual pins mounted on the planet carrier. This segmentation allows each planet gear to independently engage with the sun gear and ring gear, distributing the load and enabling the achieve high speed reduction ratios while maintaining a compact structure with reduced complexity compared to conventional multi-stage gearboxes.
Solution Approach 2:
The planetary gearbox employs a nested configuration where planet gears are positioned between the central sun gear and the outer ring gear, creating a compact nested arrangement. The planet carrier holds the planet gears within the annular space defined by the ring gear, achieving maximum space utilization and compact design that reduces overall gearbox size and complexity while maintaining effective speed reduction.
2Speed
If a reduction gearbox is added to match turbine and propeller speeds, then speed compatibility is achieved, but the engine weight increases
Solution Approach 1:
The planetary gearbox merges multiple gear functions into a single integrated assembly. The sun gear, planet gears, planet carrier, and ring gear work together as a unified mechanism to achieve both speed reduction and torque multiplication in one compact unit. This merging eliminates the need for separate multi-stage gearboxes, reducing overall weight while maintaining speed compatibility between turbine and propeller.
Solution Approach 2:
The planetary gear system provides dynamic adaptability through its ability to achieve variable speed reduction ratios by changing which component (sun gear, planet carrier, or ring gear) is held stationary and which receives input or output. This dynamic configuration allows optimization for different operating conditions, achieving speed compatibility across various flight regimes without requiring multiple fixed-ratio gearboxes, thereby reducing weight.
3Productivity
If multiple planet gear assemblies are used to achieve high speed reduction ratio, then the speed reduction efficiency is improved, but the number of moving parts and complexity increase
Solution Approach 1:
Each planet gear assembly serves multiple functions simultaneously: it transmits power from the sun gear to the ring gear, provides structural support through the planet carrier, and contributes to the overall speed reduction ratio. The planet gears also distribute radial and axial loads across multiple contact points, enhancing load-bearing capacity. This multi-functionality allows achievement of high speed reduction efficiency with a relatively simple number of moving parts.
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 configuration reduces the number of moving parts, weight, and complexity, achieving a higher speed reduction ratio with less heat generation and oil requirements, making the engine more efficient and compact.
Implementation Method 1
a plurality of planet gear assemblies, each planet gear assembly having a main gear meshed with the sun gear
Data Source
AI summary
In one aspect, there is provided a planetary gearbox, comprising a sun gear, a plurality of planet gear assemblies, each planet gear assembly having a main gear meshed with the sun gear, a fore lateral gear and an aft lateral gear disposed on opposite sides of the main gear and rotating therewith, a diameter of the main gear being different than a diameter of the fore and aft lateral gears, a planet carrier rotatably supporting at least some of the planet gear assemblies, and at least one fore ring gear meshed with the fore lateral gears, at least one aft ring gear meshed with the aft lateral gears, wherein one of the sun gear, the planet carrier, and the ring gears is configured to be operatively connected to an input, one is configured to be operatively connected to an output, and rotation of a remaining one is limited.