Compressor Shaft Bearing Mount With Extended Thread Disengagement
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Solution Overview
Problem
The existing sub-assembly for mounting a guide bearing of a high-pressure compressor shaft in turbomachines lacks sufficient axial thread length to completely disengage the interference fit between the bevel gear and the shaft tip, leading to potential damage and axial offset issues during maintenance.
Innovation Solution
A sub-assembly design featuring an axisymmetric sleeve and a nut with a blocking member having flexible legs, where the thread characteristics between the blocking member and the nut differ from those between the nut and the shaft, allowing for a longer axial thread length and preventing axial movement of the blocking member relative to the shaft, thus enabling complete disengagement without using a cylinder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the axial length of the thread between the nut and the shaft tip is extended to completely disengage the interference fit, then the bearing integrity is preserved, but the device complexity increases due to the need for additional components like a cylinder
Solution Approach 1:
The blocking member is nested within the nut structure, with its flexible legs positioned inside the nut's internal diameter. This allows the blocking member to be integrated into the existing nut assembly without requiring separate external components or complex maintenance procedures, while still providing the necessary function of preventing nut rotation during shaft extraction
Solution Approach 2:
The flexible legs of the blocking member act as an intermediary mechanism between the nut and the shaft tip thread. By engaging with the shaft tip thread and preventing relative rotation, the flexible legs enable the extended thread length to function properly for complete interference fit disengagement, thereby preserving bearing integrity without requiring additional complex components
2Ease of operation
If a cylinder is used to carry on the disengagement of the interference fit, then the complete disengagement is achieved, but axial offset between bearing rings occurs causing damage
Solution Approach 1:
The extended thread length between the nut and shaft tip enables the assembly to self-disengage the interference fit through controlled rotation during normal maintenance procedures. The blocking member prevents unwanted rotation while allowing the intended rotational movement, eliminating the need for external cylinders and preventing bearing damage from uncontrolled axial offset
Solution Approach 2:
The blocking member is pre-installed on the shaft tip before nut assembly. Its flexible legs are positioned to engage with the shaft tip thread, preliminarily establishing the constraint that prevents nut rotation. This preliminary action ensures that during subsequent maintenance operations, the extended thread can safely disengage the interference fit without causing bearing damage
3Ease of operation
If the thread length is extended to allow complete disengagement, then the interference fit is fully released, but the risk of bearing damage increases without proper blocking
Solution Approach 1:
The blocking member provides localized constraint at the nut-shaft interface through its flexible legs engaging with the shaft tip thread. This localized quality control prevents rotation at the critical interface during the disengagement process, allowing the extended thread to fully release the interference fit while protecting the bearing from damage
Solution Approach 2:
The flexible legs of the blocking member provide dynamic adaptation to the shaft tip thread geometry. They can elastically deform to accommodate manufacturing tolerances and wear, maintaining reliable engagement throughout the disengagement process. This dynamic characteristic ensures consistent prevention of nut rotation while allowing the extended thread to fully disengage the interference fit
Data Source
AI summary
A sub-assembly of a turbine engine including a shaft, a bearing for guiding an axial end of the shaft, a nut which is screw-connected to the end of the shaft and a member for blocking the rotation of the nut in relation to the end of the shaft, wherein the member for blocking the nut includes a first section bearing a plurality of flexible tabs, one end of each tab of which cooperates with a radially inner annular wall of the end of the shaft and includes a second section which cooperates with the nut, characterised in that the second section of the blocking member is screw-connected to the nut and the features of the thread between the blocking member and the nut are different from the features of the thread between the nut and the end of the shaft.