Scavenge Pump Drive Gear Tooth Profile for Constant Generator Frequency
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Solution Overview
Problem
Integrated drive generators in aircraft face challenges in maintaining a constant frequency of electric power generation due to varying input shaft speeds from gas turbine engines, which affects the scavenge/charge pump drive gear's ability to provide consistent rotational input to pumps.
Innovation Solution
A scavenge/charge pump drive gear with a gear body extending between ends, featuring a disc with radially outward gear teeth having specific roll angles and a boss with spline teeth, designed to ensure consistent rotational input to the pumps, allowing for the generation of desired constant frequency electric power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the input shaft speed varies during gas turbine engine operation, then the generator output frequency becomes variable, but maintaining constant frequency requires speed trimming mechanisms that add device complexity
Solution Approach 1:
The patent applies parameter changes by modifying the gear tooth profile parameters (roll angles A, B, C, and D) of the scavenge/charge pump drive gear. These specific roll angle parameters (A: 20.9-22.3°, B: 22.7-24.2°, C: 28.2-29.7°, D: 30.0-31.5°) are optimized to maintain consistent rotational input to the pumps despite variations in input shaft speed, thereby contributing to constant frequency output without adding complex speed trimming mechanisms.
2Reliability
If the scavenge/charge pump drive gear is designed with specific roll angles and pitch diameter tolerances, then manufacturing precision is improved, but manufacturing cost and complexity increase
Solution Approach 1:
The patent specifies precise parameter ranges for the gear tooth profile (roll angles A: 20.9-22.3°, B: 22.7-24.2°, C: 28.2-29.7°, D: 30.0-31.5°) and pitch diameter (7.87 cm ± 0.025 cm). These parameter specifications ensure consistent rotational input to the scavenge and charge pumps, improving reliability while providing clear manufacturing guidelines that balance precision requirements with manufacturability.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A scavenge/charge pump drive gear for use in an integrated drive generator has a gear body extending between a first end and a second end and having a disc extending radially outwardly. A boss extends from the disc toward the second end. There are outer gear teeth outwardly of an outer diameter of the disc. The outer gear teeth have a unique gear tooth profile with roll angles A, B, C, and D. An integrated drive generator and a method are also disclosed.