Aircraft Turbine Gear Reducer With Hydrodynamic Sun Gear Thrust Bearing
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Solution Overview
Problem
Existing mechanical reduction gears for turbomachines, particularly in aircraft, face challenges in maintaining the axial position of the sun gear while allowing radial freedom to prevent hyperstiffness, which can lead to stress concentrations and potential disengagement from satellites.
Innovation Solution
A hydrodynamic stop mechanism is introduced, utilizing an oil film between the sun gear and a bearing surface on the planet carrier to ensure axial positioning and absorb axial forces, while maintaining radial movement freedom without increasing the gearbox's axial size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a ball bearing is used to guide the solar array axially, then axial forces are absorbed effectively, but the axial size of the gearbox increases significantly
Solution Approach 1:
The patent applies hydrodynamic bearing principles by introducing oil channels that deliver lubricant to the bearing surface, forming an oil film between the solar array and the bearing surface. This hydraulic approach replaces the traditional ball bearing mechanism, enabling axial force absorption through fluid pressure while maintaining a compact axial footprint, thus resolving the contradiction between force absorption capability and axial dimension.
Solution Approach 2:
The invention changes the physical state and properties of the lubrication system by transitioning from solid contact (ball bearing) to fluid film contact (hydrodynamic bearing). By adjusting oil delivery parameters through dedicated channels and controlling the oil film thickness, the system achieves effective axial load support with significantly reduced axial dimensions compared to conventional bearing solutions.
2Reliability
If the solar element is constrained axially, then axial displacement and contact with stator are prevented, but radial freedom is reduced leading to excessive static inertia
Solution Approach 1:
The patent segments the constraint functions into two independent directions: axial constraint is provided by the hydrodynamic bearing through oil film pressure, while radial freedom is maintained by allowing the solar array to float on the oil film in the radial direction. This directional separation of constraint functions enables reliable axial positioning without excessive radial restriction, thereby preventing hyperstiffness and reducing static inertia.
Solution Approach 2:
The oil film acts as an intermediary between the solar array and the bearing surface, providing axial support through hydrodynamic pressure while allowing radial movement freedom. This fluid mediator enables the solar element to maintain axial position reliability without being overly constrained radially, thus avoiding excessive static inertia and hyperstiffness issues.
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 hydrodynamic stop effectively maintains the sun gear's axial position and absorbs operational forces, preventing stress concentrations and disengagement, while allowing radial movement to avoid hyperstiffness without increasing the gearbox's size.
Implementation Method 1
the lubrication circuit comprising at least one channel configured to deliver oil to the bearing surface and to form an oil film between the bearing surface and the solar array
Data Source
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AI summary
Mechanical reducer (60) of turbomachine (1), in particular of aircraft, this reducer comprising: - a sun gear (7) having an external toothing (7b), - a ring gear (9) which extends around the sun gear (7) and which has an internal toothing (9d), - satellites (8) which are meshed with the sun gear (7) and the ring gear (9) and which have teeth (18, 32) of different diameters, - a planet carrier (10) which supports bearings (26) for guiding the rotation of the satellites (8), and - a lubrication circuit (40) for the reducer, the planet carrier (10) comprising a hydrodynamic thrust bearing (48) for axial support of the sun gear (7).