Planetary Ring Gear Flexibility for Symmetric Starter Loading
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Solution Overview
Problem
Existing planetary gear systems in air turbine starters face challenges in ensuring symmetric gear loading, leading to uneven load distribution and potential damage during normal and overloaded operating conditions.
Innovation Solution
A flexible ring gear with bridges and cantilevers is integrated into the planetary gear system, allowing for deflection and absorption of eccentricity and uneven loads, distributing loads symmetrically and preventing damage by deflecting under load, similar to a conventional solid ring gear during overloads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional solid ring gear is used in the planetary gear system, then the structure is simple and rigid, but the load distribution among planetary gears is uneven and peak loads on gear teeth are high
Solution Approach 1:
The ring gear is segmented into multiple independent bridges connecting the inner and outer portions. These bridges are spaced circumferentially around the ring gear, creating discrete load paths that allow each bridge to deflect independently under load, thereby distributing forces more evenly across all planetary gear interfaces.
Solution Approach 2:
The ring gear transitions from a rigid solid structure to a dynamic flexible structure. The bridges are designed with specific flexibility characteristics that allow them to deflect under loading conditions, enabling the ring gear to adapt its load distribution in real-time based on the operating conditions and planetary gear positions.
2Strength
If the ring gear is made flexible with bridges, then load distribution is improved and peak loads are reduced, but the structural complexity increases
Solution Approach 1:
The ring gear employs a flexible shell structure composed of thin bridge elements that connect the inner and outer portions. These bridges are designed with appropriate thickness and material properties to provide the necessary flexibility while maintaining structural integrity, allowing the ring gear to deform elastically under load without permanent deformation.
Solution Approach 2:
The ring gear utilizes composite construction combining rigid regions (inner and outer portions) with flexible regions (bridges). This composite structure allows different parts of the ring gear to have different mechanical properties - the inner and outer portions provide structural support and mounting surfaces, while the bridges provide flexibility and load distribution.
3Reliability
If the bridges deflect under loading, then eccentricity and uneven loads are absorbed, but the manufacturing precision requirements increase
Solution Approach 1:
The bridge geometry parameters (cross-sectional area, length, thickness, material properties) are carefully selected and optimized to achieve the desired flexibility characteristics. By adjusting these parameters, the ring gear can be tuned to provide appropriate load distribution and eccentricity absorption while maintaining manufacturability with standard tolerances.
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 flexible ring gear design enhances load distribution, reduces wear on gearbox components, and increases the operating life of the starter by absorbing distortions and eccentricities, while maintaining efficiency and reducing peak loads on gear teeth.
Implementation Method 1
the flexible ring gear includes a set of bridges located between the set of slots and coupling the radially inner portion and the radially outer portion, wherein at least one bridge of the set of bridges is configured to deflect under loading from at least one of the set of planetary gears
Implementation Method 2
A turbine member is journaled within the housing and disposed within the flow path for rotatably extracting mechanical power from the flow of gas
Data Source
Figure 1
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AI summary
The air turbine starter 10 includes a housing 30 defining an inlet 32, an outlet 34, and a flow path extending between the inlet 32 and the outlet 34 for communicating a flow of gas there through. A turbine member 38 is journaled within the housing 30 and disposed within the flow path for rotatably extracting mechanical power from the flow of gas and having a turbine output shaft. The air turbine starter 10 further includes a planetary gear system 44 drivingly coupled with the turbine output shaft and including a sun gear 70, 170, 270, a ring gear 46, 82, 182, 282 mounted to the housing 30, and a set of planetary gears 48 operably coupling the sun gear 70, 170, 270 and the ring gear 46, 82, 182, 282 with the sun gear 70, 170, 270 is coupled to the turbine output shaft.