Aircraft Engine Shaft Assembly With Guide Teeth for Spline Alignment
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Solution Overview
Problem
The assembly of turbomachine shafts is challenging due to the heavy upstream module, which can cause misalignment and damage to splines during engagement, especially when assembled horizontally, leading to potential cracks and increased inspection/validation work.
Innovation Solution
A set of shafts with internal and external guide teeth that ensure centering during assembly, allowing for axial alignment and preventing contact between spline ends, with the teeth designed to absorb shocks and stresses without transmitting torque, thus protecting the splines and ensuring precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the upstream module is assembled horizontally, then the assembly process is simplified, but the heavy reducer causes fan shaft deformation and spline misalignment
Solution Approach 1:
The patent applies preliminary action by providing guide teeth on the shafts before the actual spline engagement. These guide teeth pre-align the shafts during the approach phase, ensuring that when the splines eventually engage, they are already properly positioned. This prevents misalignment caused by the heavy reducer's deformation during horizontal assembly.
2Manufacturing precision
If the modules are assembled vertically, then spline misalignment is reduced, but the assembly process becomes more complex
Solution Approach 1:
The guide teeth act as an intermediary element between the shafts during assembly. They mediate the alignment process by providing a controlled engagement path that guides the shafts into proper position before the main splines engage, thus achieving vertical assembly precision benefits while maintaining horizontal assembly convenience.
3Device complexity
If the splines are engaged directly without guide teeth, then the device complexity is reduced, but the risk of spline damage during assembly increases
Solution Approach 1:
The patent applies segmentation by dividing the engagement function into two distinct parts: guide teeth for alignment and splines for torque transmission. The guide teeth are axially separated from the splines, allowing the shafts to be aligned first through the guide teeth, and only then do the splines engage for full torque transmission. This segmentation protects the splines from damage during the alignment phase.
Solution Approach 2:
The guide teeth perform the preliminary alignment action before the splines engage. By providing a dedicated alignment mechanism that operates first, the splines are protected from misalignment stresses and potential damage that would occur if they had to perform both alignment and torque transmission functions simultaneously.
4Power
If guide teeth are designed to transmit torque, then the torque transmission capability is improved, but the risk of tooth damage during assembly increases
Solution Approach 1:
The patent clearly segments the functions: guide teeth for alignment only, and splines for torque transmission. The guide teeth are axially separated from the splines by a distance that prevents torque transmission during the alignment phase. This segmentation ensures the guide teeth are not subjected to torque loads they are not designed to handle, protecting their durability.
Solution Approach 2:
The guide teeth and splines have different local qualities and designs optimized for their specific functions. The guide teeth are positioned and dimensioned for alignment, while the splines are designed for torque transmission. This local differentiation ensures each element performs its intended function reliably without being overloaded.
Data Source
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AI summary
A shaft assembly (22, 32) for an aircraft turbine engine (1), comprising a first outer shaft (32) and a second inner shaft (22), the first outer shaft being intended to be engaged axially on the second shaft and comprising inner longitudinal splines (34) for coupling with outer longitudinal splines (24) of the second shaft, characterised in that, when the first and second shafts are in the coupling position, the inner and outer splines are engaged in one another and cooperate with each other in an axial coupling area (Z), the inner and outer teeth being situated outside this coupling area.