Rotor Shaft Locking Assembly With Retainer Anti-Loosening Fit
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Solution Overview
Problem
Existing locking assemblies for air turbine starters, such as those used in gas turbine engines, often require expensive customized nuts and lengthy assembly times, necessitating additional components like shims to achieve secure compression and balancing.
Innovation Solution
A locking assembly comprising a rotor shaft with an inner bore, a gear mounted on its outer diameter, a lock nut threadedly engaged with the rotor shaft, and a retainer with a projection portion that biases the lock nut against the gear, establishing an interference fit to secure the gear and bearing assembly to the rotor shaft, reducing the likelihood of the lock nut loosening during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing locking assemblies use customized nuts and additional components like shims, then secure compression and balancing are achieved, but assembly complexity increases and assembly time lengthens
Solution Approach 1:
The retainer combines multiple functions into a single component: it provides interference fit with the rotor shaft for retention, includes a projection portion that biases the lock nut against the gear for compression, and integrates the locking mechanism. This eliminates the need for separate customized nuts and shims, reducing assembly complexity while maintaining secure compression and balancing
Solution Approach 2:
The retainer serves multiple purposes simultaneously: it acts as a mounting component with interference fit for the rotor shaft, a compression mechanism through its projection portion biasing the lock nut, and a retention device. This multi-functionality reduces the number of components needed while achieving the same reliability goals
2Reliability
If existing locking assemblies use customized nuts and additional components, then secure retention is achieved, but assembly time increases
Solution Approach 1:
The retainer is pre-configured with the interference fit dimensions and projection portion geometry during manufacturing. During assembly, the retainer is simply inserted into the rotor shaft bore and the lock nut is threaded on, with the projection portion automatically providing the biasing force. This preliminary design work eliminates the need for time-consuming assembly of multiple customized components
Solution Approach 2:
By combining the retention function (interference fit), compression function (projection portion biasing lock nut), and locking function into a single retainer component, the assembly process is simplified to installing one piece rather than assembling multiple customized components, significantly reducing assembly time
3Device complexity
If a lock nut is used without additional retention mechanisms, then assembly is simplified, but the likelihood of lock nut loosening during operation increases
Solution Approach 1:
The projection portion of the retainer is designed to continuously bias the lock nut against the gear in the direction opposite to the loosening force. This preliminary counteracting force prevents the lock nut from loosening during operation, maintaining reliability while keeping the assembly simple
Solution Approach 2:
The retainer's projection portion automatically provides the biasing force needed to prevent lock nut loosening as part of its interference fit installation. The system is self-regulating, requiring no additional active components or complex mechanisms to maintain the anti-loosening function
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 solution simplifies assembly, reduces the risk of lock nut loosening, and provides secure retention of the gear and bearing assembly, enhancing operational reliability and reducing assembly complexity and potential misbalance.
Implementation Method 1
a projection portion extending from the step portion. The projection portion is insertable into the inner bore to bias the lock nut against the axial end face of the gear
Implementation Method 2
the step portion is dimensioned to establish an interference fit with the rotor shaft along the inner bore
Data Source
AI summary
An assembly for a coupling together rotatable components according to an example of the present disclosure includes, among other things, a rotor shaft extending along a centerline axis, the rotor shaft defining an inner bore extending from an axial end of the rotor shaft, a gear mounted on an outer diameter of the rotor shaft, a lock nut threadedly engaged with the outer diameter of the rotor shaft such that the lock nut abuts against an axial end face of the gear, and a retainer including a step portion extending from a head portion and including a projection portion extending from the step portion. The projection portion is insertable into the inner bore to bias the lock nut against the axial end face of the gear, and the step portion is dimensioned to establish an interference fit with the rotor shaft along the inner bore. A starter assembly and a method of assembly are also disclosed.