Split-Ring Bearing Retention for Axial Shaft Displacement
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Solution Overview
Problem
Shafts in VTOL aircraft, subjected to high loads and extreme conditions, experience axial displacement due to bending moments and negative thrust, leading to wear and damage in press-fit bearing systems, which can cause self-disassembly and additional component damage.
Innovation Solution
A bearing retention system featuring a recess with a conical, transition, and curved surface on the shaft, combined with a split ring and locking ring assembly, securely axially positions the bearing within the gearbox, preventing axial displacement and minimizing weight addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a press-fit bearing system is used on the shaft, then the bearing can be mounted between the shaft and housing, but axial displacement occurs due to bending moments and negative thrust causing wear and damage
Solution Approach 1:
The bearing retention system is divided into multiple functional segments: a bearing assembly (with inner race, outer race, and rollers), a retention assembly (with split ring and locking ring), and a shaft with recess. This segmentation allows each component to perform its specific function - the bearing supports radial loads while the retention assembly prevents axial displacement, resolving the contradiction between bearing mounting and axial stability.
Solution Approach 2:
The split ring is nested within a recess formed in the shaft, and the locking ring surrounds the split ring. This nested configuration allows the retention components to be compactly integrated with the shaft and bearing assembly, preventing axial displacement without adding excessive external complexity or weight.
2Reliability
If a retention system is added to prevent axial displacement, then bearing security is improved, but device complexity increases
Solution Approach 1:
The split ring is designed with flexibility to radially expand and contract. During assembly, the split ring can be compressed radially to fit into the recess, then it expands to engage with the shaft surface. This dynamic behavior allows the retention system to secure the bearing axially while maintaining a relatively simple structure that adapts to the shaft geometry.
Solution Approach 2:
The split ring acts as an intermediary component between the shaft and the bearing assembly. It translates the radial constraint of the recess into axial retention force, mediating the interaction between these components and preventing axial displacement without requiring direct complex mechanical engagement between the shaft and bearing.
3Reliability
If a retention assembly is installed to secure the bearing, then axial displacement is prevented, but weight is added to the shaft system
Solution Approach 1:
The split ring is constructed as a thin, flexible metallic shell that can radially expand and contract. This thin-walled structure provides the necessary axial retention capability while minimizing the added weight. The flexibility allows it to be installed in a compact configuration within the shaft recess without requiring excessive material.
4Adaptability or versatility
If the shaft is subjected to high loads and extreme conditions, then the aircraft can operate under demanding conditions, but axial displacement and self-disassembly occur
Solution Approach 1:
The retention assembly (split ring and locking ring) is pre-installed on the shaft before the bearing assembly is mounted. This preliminary action creates a mechanical constraint that prevents axial displacement of the bearing under high loads and extreme conditions, countering the potential for self-disassembly before it can occur during operation.
Data Source
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AI summary
A gear box includes a housing, a shaft that is driven by the gear, the shaft including a recess, a bearing mounted between the shaft and the housing to support the shaft for rotation with respect to the housing about a rotation axis, and a ring assembly for axially securing the bearing to the shaft. The ring assembly surrounds the shaft and is seated in the recess. The recess has a retaining surface including a conical surface extending at an angle to the rotation axis, a curved surface, and a transition surface extending between the conical surface and the curved surface, the transition surface extending generally parallel to the rotation axis.