Aircraft Turbine Gearbox Bearing Layout for Compact Planet Support
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Solution Overview
Problem
Double-stage mechanical reduction gears in turbomachines are asymmetrical, leading to non-negligible moments and increased size and mass, which negatively impact performance due to the need for symmetrical bearing arrangement around satellites, causing elongation and increased drag.
Innovation Solution
The configuration of rolling bearings between the teeth of the second toothing and a plane perpendicular to the axis of rotation, allowing for reduced axial dimension and mass of the planet carrier and reducer, with the bearings interposed axially between the series of teeth and the plane, rather than at the axial ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If symmetrical bearing arrangement around satellites is used, then reliability and support are improved, but axial dimension and mass increase
Solution Approach 1:
The patent applies asymmetry by positioning the two roller bearings at different axial locations relative to the satellite's median plane. One bearing is positioned upstream and the other downstream, creating an asymmetric arrangement that maintains proper satellite support while reducing the overall axial dimension of the reducer compared to symmetric bearing placement.
Solution Approach 2:
The patent redistributes bearing positions along the axial dimension, placing bearings between the teeth of the second toothing and the median plane rather than at axial ends. This dimensional repositioning allows for compact axial layout while maintaining effective satellite support and guidance.
2Stability of the object's composition
If symmetrical bearing arrangement around satellites is used, then stability is improved, but mass increases
Solution Approach 1:
The asymmetric bearing arrangement with one bearing upstream and one downstream of the median plane provides stable satellite support while minimizing the mass of the reducer by eliminating the need for excessive axial length that would be required for symmetric bearing placement.
3Length of moving object
If reduced axial dimension is achieved, then motor size and drag are minimized, but bearing arrangement complexity increases
Solution Approach 1:
The bearing arrangement is segmented into two distinct positions: one bearing positioned upstream between the teeth and the median plane, and the other bearing positioned downstream between the teeth and the median plane. This segmentation allows for compact axial dimension while maintaining clear functional separation of the bearing roles.
4Power
If asymmetrical double-stage gearbox is used, then reduction ratio is achieved, but moments and vibrations increase
Solution Approach 1:
The patent employs asymmetric bearing positioning to counterbalance the inherent asymmetry of the double-stage gearbox. By strategically placing one bearing upstream and one downstream of the median plane, the design compensates for uneven moment distribution and reduces vibrations generated by the asymmetrical gear arrangement.
Solution Approach 2:
The asymmetric bearing arrangement acts as a counterbalancing mechanism, with bearings positioned to offset the harmful moments and vibrations generated by the asymmetrical double-stage reduction gear configuration.
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 significantly reduces the axial dimension and mass of the reducer, enhancing the overall performance by minimizing the size and drag of the motor while maintaining effective support and guidance of satellites.
Implementation Method 1
each satellite being centered and guided in rotation around its axis vis-à-vis the satellite carrier by roller bearings
Implementation Method 2
The gearbox's satellites must be supported and guided in rotation relative to the satellite carrier. The conventional solution for this is to use bearings.
Data Source
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AI summary
A mechanical gearbox (160) for a turbomachine (1), particularly an aircraft, comprising: - a sun gear (70) having an axis (X) of rotation, - a ring gear (90) extending around the sun gear (70), - planet gears (80) meshed with the sun gear (70) and the ring gear (90), each comprising a first set of teeth (84) and a second set of teeth (84), each set having two rows of teeth situated on either side of a median plane (H), each of the planet gears (80) being centered and guided in rotation by bearings (94a, 94b), including an upstream bearing (94a) axially interposed between the upstream row of teeth (84d1) of the second set of teeth (84) and said plane (H), and a downstream bearing (94b) axially interposed between the downstream row of teeth (84d2) of the second set of teeth (84) and said plane (H). (H).