Boron-Diffused Slotted Bearings for Geared Turbofan Gearbox Mounting
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Solution Overview
Problem
Load slot bearings in high-temperature applications and critical linkage scenarios, such as geared turbofan engines, face issues with wear, galling, and fretting due to improper maintenance and inadequate surface hardness, leading to reduced bearing life and performance.
Innovation Solution
A load slot bearing system comprising a cobalt alloy ball and a precipitation-hardenable alloy outer race with boron diffusion case hardening, along with anti-galling coatings and precise slot design for enhanced wear resistance and lubrication, ensuring effective interaction between the ball and the race.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional heat treat case hardening processes are used to produce bearing elements with different hardnesses, then manufacturing complexity is reduced, but wear resistance and surface morphology characteristics are insufficient leading to galling and fretting
Solution Approach 1:
The patent applies boron diffusion treatment specifically to the engagement surfaces of the ball and outer race, creating a hard, wear-resistant surface layer only where contact occurs. The core material retains its toughness while the surface gains exceptional wear resistance. This localized treatment resolves the contradiction by providing high wear resistance at contact surfaces without requiring complex case hardening of entire bearing elements.
Solution Approach 2:
The patent changes the surface chemistry and microstructure by diffusing boron into the engagement surfaces, fundamentally altering the material properties at the contact interface. This parameter change creates a surface layer with dramatically improved hardness and wear resistance while maintaining the base material's ductility, resolving the contradiction between wear resistance and manufacturing simplicity.
2Duration of action of moving object
If maintenance intervals are extended or maintenance is deferred, then operational time increases, but bearing wear increases and bearing life is compromised
Solution Approach 1:
The boron diffusion treatment is applied during manufacturing as a preliminary action, pre-establishing a wear-resistant surface layer before the bearing enters service. This preliminary protective action allows the bearing to operate for extended periods without maintenance, as the pre-hardened surface resists wear and prevents galling that would otherwise require frequent lubrication or replacement.
Solution Approach 2:
The hardeneng surface layer created by boron diffusion provides self-protecting properties, where the bearing surface automatically resists wear and maintains its morphology without requiring external intervention. This self-service characteristic enables extended operational periods between maintenance intervals, as the bearing protects itself through its inherently wear-resistant surface.
3Device complexity
If insufficient lubrication is provided, then device complexity is reduced, but galling and fretting increase leading to premature bearing failure
Solution Approach 1:
The patent extracts the lubrication function from the operational requirements by creating a surface that inherently resists adhesion and wear through boron diffusion. The engagement surfaces are modified to eliminate the need for continuous lubrication, taking out the dependency on lubrication systems and their associated complexity while maintaining reliable bearing operation.
Solution Approach 2:
The boron-diffused surface layer acts as a permanent protective coating that replaces the need for recurring lubrication maintenance. Instead of relying on consumable lubricants that require periodic replenishment, the surface treatment provides long-lasting wear protection that eliminates ongoing lubrication complexity.
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 system maintains desired morphological surface characteristics, reduces wear and galling, and extends bearing life by providing improved wear resistance and corrosion resistance, suitable for high-temperature applications like geared turbofan engines.
Implementation Method 1
At least one of the outer engagement surface of the inner member or the inner engagement surface of the outer member has boron diffused therein
Implementation Method 2
an outer member comprising a precipitation-hardenable alloy
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A load slot bearing system for a mounting system for a gearbox on a geared turbofan engine includes a load slot bearing assembly (10) having a cobalt alloy inner member (12) and a precipitation-harden- able alloy outer member (14). The inner member (12) defines an outer engagement surface (18) and the outer member (14) defines an inner engagement surface (22) slidably and rotatably engaged with the- outr engagement surface (18). One of the outer engagement surface (18) or the inner engagement surface (22) has boron diffused therein. The load slot bearing system includes first and second slots (20) extending inward from a face (21) defined by the outer member (14), the second slot being positioned generally diametrically opposite the first slot. A first element (44) is located in the bore (16) of the inner member (12) of the load slot bearing assembly (10) and is connected to the inner member (12). A second element (46) is connected to the outer member (14) of the load slot bearing assembly (10).