Coaxial Shaft Gear Assembly With Landmark Alignment for Low Backlash
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Solution Overview
Problem
Gas turbine engines with twin-spool configurations face challenges in increasing speed differential between shafts due to limited space, as well as installation complexities and backlash issues with traditional gear assemblies, which affect durability and efficiency.
Innovation Solution
A gear assembly comprising an input gear, an output gear, and a pair of idler gear shafts with two stages of speed change, where the idler gear shafts are aligned using landmarks to minimize backlash and optimize alignment during assembly, allowing for efficient speed transmission between coaxial turbine and compressor shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional gear assemblies are used to increase speed differential between shafts, then speed transmission is achieved, but the assembly becomes too voluminous and complex
Solution Approach 1:
The gear assembly is divided into modular components including input gear, output gear, and multiple idler gear shafts that can be independently positioned and assembled. This segmentation allows for compact arrangement while achieving the required speed differential without increasing overall assembly complexity
Solution Approach 2:
The idler gear shafts are arranged concentrically between the input and output gears, with each idler gear shaft nested within the radial space of the other components. This nesting approach maximizes space utilization and achieves high speed differential in a compact volume
2Power
If traditional gear assemblies are installed to achieve speed change, then torque transmission is achieved, but backlash affects gear durability
Solution Approach 1:
Landmarks are provided on the input gear, output gear, and idler gear shafts to establish precise alignment references before assembly. This preliminary alignment feature ensures that when components are assembled, the gears mesh with minimal backlash, improving durability while maintaining torque transmission capability
Solution Approach 2:
The invention replaces traditional mechanical adjustment methods for eliminating backlash with a landmark-based alignment system. This substitution provides more consistent and reliable gear meshing without requiring complex mechanical adjustment mechanisms
3Ease of manufacture
If more space is allocated for gear assembly to reduce complexity, then ease of assembly is improved, but space availability in gas turbine engine is limited
Solution Approach 1:
The idler gear shafts are arranged in different axial positions between the input and output gears, utilizing the axial dimension to separate components that would otherwise compete for radial space. This dimensional arrangement maintains ease of assembly while fitting within limited engine space
Data Source
AI summary
A gear assembly for a gas turbine engine has an input gear adapted to be secured to a turbine shaft. An output gear is adapted to be secured to a compressor shaft, the input gear and the output gear having the same number of teeth. A pair of idler gear shafts is provided, each said idler gear shaft having a first stage gear meshed with the input gear to be driven by the turbine shaft at a first stage of speed change. A second stage gear is axially spaced from the first stage gear and rotates with the first stage gear. The second stage gear is meshed with the output gear to drive the compressor shaft at a second stage of speed change. Landmarks are provided for aligning the gears during assembly in a desired orientation.