Fan Gear Drive Lubrication With Spherical Bearings for Vibration Relief
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Solution Overview
Problem
The fan drive gear system in gas turbine engines, particularly in helicopter applications, faces failures due to vibrational stresses caused by the cantilevered support of intermediate gears on an integrated torque frame with conventional rolling element bearings.
Innovation Solution
A lubrication system is introduced that includes a torque frame with integrated shafts and a non-structural oil baffle providing lubrication passages and bearing assemblies with spherical bearings, allowing for efficient lubrication delivery to gear surfaces through radially extending passageways, reducing the need for high-strength materials and minimizing stress on the torque frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional rolling element bearings are used in cantilevered support, then the gear system can be compactly arranged, but vibrational stresses increase causing torque frame failure
Solution Approach 1:
The patent changes the bearing type from conventional rolling element bearings to spherical bearings, which can accommodate angular misalignment and reduce vibrational stresses. This parameter change in bearing geometry and functionality resolves the contradiction by maintaining compact arrangement while improving torque frame reliability through reduced stress concentrations.
Solution Approach 2:
The spherical bearings provide dynamic adaptability by allowing angular movement, enabling the bearing assembly to self-adjust to vibrational loads rather than rigidly resisting them. This dynamic capability reduces stress on the torque frame while maintaining the compact cantilevered support structure.
2Strength
If high strength metallic alloys are used for the carrier, then the torque frame strength increases, but the weight and complexity of the system increases
Solution Approach 1:
The patent changes the bearing type to spherical bearings that can accommodate angular misalignment, which reduces the stress concentrations and dynamic loads on the torque frame. This allows the use of lighter materials or thinner sections while maintaining adequate strength, thereby reducing weight without sacrificing torque frame strength.
3Device complexity
If conventional bearing assemblies are used, then the gear system structure is simplified, but lubrication delivery to bearing surfaces is insufficient
Solution Approach 1:
The bearing assembly is segmented into modular components with integrated lubrication passages. The spherical bearing, race, and lubrication channels are designed as integrated units that can be independently supplied with lubricant, allowing simple modular assembly while ensuring reliable lubrication delivery to all bearing surfaces through dedicated passageways.
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 lubrication system effectively reduces vibrational stresses and extends the lifespan of the torque frame by ensuring consistent lubrication to the gear bearings, enhancing the reliability and durability of the fan drive gear system.
Implementation Method 1
each shaft, spherical bearing and race respectively include radially extending first, second and third passageways that are aligned with one another and in fluid communication with the lubrication passage to deliver lubricating fluid from the lubrication passage to bearing surfaces provided between the race and the respective gear
Data Source
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AI summary
A fan gear drive system includes a torque frame (56) having a base (61) with integrated gear shafts (58) circumferentially spaced relative to one another. A fan shaft (34) is integrated with the base (61), such that the torque frame (56) provides rotational output from the fan gear drive system. Each shaft provides a shaft axis. A bearing assembly (60) is mounted on each of the gear shafts (58). The bearing assembly includes a spherical bearing (88) configured to permit angular movement of the bearing axis relative to the shaft axis.