Planet Carrier Pylon Stiffness Layout for Gear Misalignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in designing an epicyclic gearbox for aeronautic applications is to create a reliable and compact unit that reduces planet gear misalignment during torque extraction, while minimizing the need for oversized components, which is typically addressed by increasing gear size or limiting the number of planet gears, both of which have limitations in terms of space and efficiency.
Innovation Solution
A planet-carrier design featuring a side plate, central ring, and support pylons with a stiffness-reducing feature, where the side-plate stiffness is significantly greater than the pillar stiffness, and the pillar stiffness is greater than the feature stiffness, and the support pylons form an angle with the side plate between 20° and 90°, ensuring equal load sharing and minimizing misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the size of epicyclic gearbox components is increased to counteract planet gear misalignment during torque extraction, then planet gear alignment is improved, but the gearbox size and weight increase
Solution Approach 1:
The invention applies local quality by creating an asymmetric support pylon structure where the first portion has different stiffness characteristics than the second portion. The first support pylon includes a first pillar with specific stiffness and a first stiffness-reducing feature, while the second support pylon includes a second pillar with different stiffness and a second stiffness-reducing feature. This localized variation in structural properties allows precise control over load distribution and planet gear alignment without increasing overall gearbox size.
Solution Approach 2:
The invention changes physical parameters by introducing stiffness-reducing features (such as reliefs or cavities) in specific locations on the support pylons. These features modify the local stiffness parameters of the carrier structure, allowing the first support pylon to have controlled flexibility to accommodate misalignment while the second support pylon maintains higher stiffness for stable support. This parameter modification enables proper gear alignment without oversizing the entire gearbox.
2Volume of moving object
If the number of planet gears is limited to three pairs to leave space for planet-carrier reinforcement, then component reinforcement space is improved, but torque handling capability and efficiency deteriorate
Solution Approach 1:
The asymmetric support pylon design with differentiated stiffness characteristics enables the carrier to properly support a higher number of planet gears (five to nine pairs) by locally managing the load distribution. The first support pylon with reduced stiffness accommodates the misalignment caused by torque extraction, while the second support pylon with higher stiffness provides stable support, allowing more planet gears to be fitted without compromising either reinforcement space or torque handling capability.
3Manufacturing precision
If asymmetric support structures are used to accommodate misalignment, then planet gear alignment is improved, but device complexity increases
Solution Approach 1:
The invention segments the support pylon structure into distinct first and second support pylons with different stiffness characteristics. Each pylon is further segmented into a pillar portion and a stiffness-reducing feature portion. This segmentation allows independent optimization of each segment's properties to achieve proper load distribution while keeping the overall structure manageable and manufacturable through standardized features.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An apparatus and method for reducing planet gear misalignment of planet gears mounted on a planet-carrier in an epicyclic gearing. The apparatus and method of the present disclosure specifically provide for a stiffness-reducing feature, a pillar, and a side-plate, each with a respective stiffness. In several embodiments, the feature stiffness is less than the pillar stiffness which is at least 10% less than the side-plate stiffness. The stiffness-reducing feature and the pillar may make up a pylon which has an axis. The pylon axis may form an angle with the side plate which is less than 90° and greater than 20°.