Planet Gear Hydrodynamic Bearing Layout for Compact Reduction Gears
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Mechanical reduction gears for turbomachines, particularly in aircraft, face challenges with large axial dimensions due to the need to accommodate high loads and centrifugal effects, leading to increased size and power losses associated with hydrodynamic bearings used to guide planet gears.
Innovation Solution
The use of two independent hydrodynamic bearings, one on either side of a median plane, to guide each planet gear, reducing axial dimensions, oil flow requirements, and susceptibility to misalignment, while maintaining the required load capacity and reducing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single long hydrodynamic bearing is used to guide planet gears, then the load capacity is sufficient, but the axial dimension increases and power losses increase
Solution Approach 1:
The single long hydrodynamic bearing is divided into two separate shorter bearings arranged axially. Each bearing has a cylindrical body engaged in the planet gear, with the first bearing having a first cylindrical surface and the second bearing having a second cylindrical surface. This segmentation reduces the axial dimension while maintaining load capacity through distributed support.
2Strength
If a single long hydrodynamic bearing is used to guide planet gears, then the load capacity is sufficient, but power losses increase due to high oil flow rates
Solution Approach 1:
The bearing system is segmented into two independent bearings with separate oil supply and discharge paths. The first bearing has a first oil supply and first oil discharge, while the second bearing has a second oil supply and second oil discharge. This allows optimized oil flow distribution that reduces overall power losses while maintaining sufficient lubrication for the load capacity.
3Length of moving object
If the axial dimension is reduced by using shorter bearings, then the compactness improves, but the load capacity may be insufficient
Solution Approach 1:
Instead of using one long bearing, the system employs two shorter bearings in series, each contributing to the overall load capacity. The first bearing supports a portion of the axial load and the second bearing supports the remaining portion, collectively providing sufficient load capacity while reducing the total axial dimension.
Solution Approach 2:
The load-bearing function is merged across two separate bearing components. The first cylindrical surface and second cylindrical surface work together to provide the total load capacity required, combining the support functions of multiple elements to achieve the necessary strength in a more compact arrangement.
4Stability of the object's composition
If a single long bearing is used, then alignment stability may be compromised, but using shorter bearings requires precise positioning
Solution Approach 1:
The bearing system is segmented into two independent units, each with its own cylindrical body engaged in the planet gear. This segmentation allows each bearing to be independently positioned and aligned, potentially improving overall alignment stability while distributing the positioning requirements across two components rather than one.
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 allows for a more compact and efficient mechanical reduction gear design with reduced oil flow rates and lower power losses, while maintaining the necessary load-bearing capacity and alignment stability.
Implementation Method 1
a bearing comprising a body that engages a planet gear and around which a pressurised oil film is located
Implementation Method 2
the bearings that support the planet gears and guide them in rotation are loaded and there is little room to integrate them without considerably increasing the size of the reduction gear... by the centrifugal effects applied to the planet gears
Data Source
AI summary
A mechanical reduction gear for a turbomachine, in particular for an aircraft, the reduction gear including a sun gear, a ring gear, planet gears which are meshed with the sun gear and the ring gear, hydrodynamic bearings for guiding the planet gears in rotation, these bearings being carried by a planet carrier and including cylindrical bodies which are engaged in the planet gears and which are configured so as to be supplied with oil and so as to form guiding oil films between the bodies and the planet gears, wherein each of the planet gears is guided by two hydrodynamic bearings independent of each other and disposed on either side of the plane.