Planet Gear Journal Pin Interference Fit for High-Torque Gearboxes
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Solution Overview
Problem
Turbine engine gearbox assemblies face challenges in maintaining a sufficient interference fit between the journal pin and planet carrier to prevent slippage and plastic deformation, especially under increasing torque and power demands, leading to efficiency and power output issues.
Innovation Solution
The design incorporates a specific interference ratio range for the journal pin and planet carrier, defined by the relationships between fan torque, gear ratio, and material properties to ensure the interference fit is neither too tight nor too loose, using equations to determine the minimum and maximum interference ratios to prevent slippage and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the interference fit between journal pin and planet carrier is increased to prevent slippage, then the torque transmission capability is improved, but the risk of plastic deformation increases
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships for the interference ratio based on material properties, torque requirements, and geometric parameters. The interference ratio is defined as a function of the yield strength of the journal pin and planet carrier materials, the torque to be transmitted, and the dimensions of the journal pin and planet carrier, allowing optimization of the interference fit to prevent both slippage and plastic deformation
Solution Approach 2:
The patent introduces dynamic considerations by accounting for variable operating conditions including varying torque loads, rotational speeds, and temperature effects on material properties. The interference fit design incorporates safety factors and allows for thermal expansion effects, making the system adaptable to changing operational demands while maintaining reliable torque transmission
2Force
If the interference fit is made tighter to prevent slippage under high torque, then the torque transmission is improved, but component stress and deformation increase
Solution Approach 1:
The patent uses parameter changes by defining the interference ratio as a function of multiple parameters including material yield strength, applied torque, journal pin diameter, and planet carrier dimensions. This allows the interference fit to be precisely calibrated to transmit required torque while keeping stresses within acceptable limits through mathematical optimization
Solution Approach 2:
The patent incorporates feedback mechanisms by establishing design criteria that require verification of stress levels against material yield strength. The interference ratio is determined through an iterative process that checks both sufficient torque transmission and acceptable stress levels, allowing design adjustments based on calculated stress feedback
3Reliability
If the interference ratio is increased to prevent slippage, then the reliability of torque transfer is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent addresses manufacturing precision challenges by defining the interference ratio in terms of measurable geometric parameters and material properties. The design provides specific tolerance recommendations based on the calculated interference ratio, allowing manufacturers to achieve reliable torque transfer with practical manufacturing capabilities through parameter-based design guidance
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
This approach allows for a more efficient and reliable gearbox assembly that effectively transfers kinetic energy from the turbine shaft to the fan shaft, improving power output and reducing the risk of component failure due to excessive stress.
Implementation Method 1
the coupling of the journal pin and the planet carrier is characterized by an interference ratio greater than a minimum interference ratio of 1.0e-5
Data Source
AI summary
A gearbox assembly for a turbine engine. The turbine engine includes a drive shaft and a fan shaft. The gearbox assembly includes a first gear, a second gear, an output, and a journal pin. The first gear is connected to the drive shaft. The second gear is supported by a planet carrier. The output is connected to the fan shaft. Torque is transferred from the drive shaft of the core turbine engine to the fan shaft through the gearbox assembly. The journal pin is inserted into the planet carrier. The second gear rotates about the journal pin. A coupling of the journal pin and the planet carrier is characterized by an interference ratio greater than a minimum interference ratio of 1.0e-5.