Accessory Drive Gear Tooth Profile for Stable 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 accessory drive gear's ability to provide consistent rotational input to driven gears, impacting the operation of accessory systems like pumps.
Innovation Solution
A method for replacing the accessory drive gear in an integrated drive generator with a new gear design featuring specific roll angles and dimensions, including a gear body with gear teeth extending from the forward to the rear end, and a unique gear tooth profile to ensure consistent rotational input, along with a method for installing this gear to maintain desired frequency and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the input shaft speed varies during gas turbine engine operation, then the generator can adapt to different engine speeds, but the generated power frequency becomes variable instead of constant
Solution Approach 1:
The patent applies dynamics by making the ring gear position adjustable relative to the differential carrier. The ring gear can be positioned at different angular positions around the carrier perimeter, allowing the system to dynamically adapt to varying engine speeds while maintaining constant output frequency. This is achieved through a mechanism that permits radial movement of the ring gear assembly relative to the carrier, enabling real-time adjustment of the gear ratio to compensate for input speed variations.
2Ease of manufacture
If the accessory drive gear uses conventional gear tooth profiles, then the design and manufacturing are simpler, but the rotational input to driven gears is inconsistent affecting accessory system operation
Solution Approach 1:
The patent applies parameter changes by modifying the gear tooth profile parameters, specifically the roll angles during gear tooth generation. The gear teeth are formed with specific roll angle ranges (17-22 degrees at the pitch circle, 27-32 degrees at the outer diameter) to optimize the meshing characteristics. This results in more consistent rotational input to driven gears and improved performance of accessory systems while remaining manufacturable with standard gear cutting processes.
3Reliability
If the accessory drive gear is designed with specific roll angles and dimensions, then the rotational input consistency improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies optimized parameter ranges for gear tooth generation (roll angles of 17-22 degrees at pitch circle, 27-32 degrees at outer diameter) that balance manufacturing precision requirements with performance benefits. These parameter ranges are designed to achieve consistent rotational input while remaining achievable with conventional gear manufacturing processes, avoiding excessively tight tolerances that would make production impractical.
Data Source
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AI summary
An accessory drive gear (29) for use in the integrated drive generator includes a gear body extending between a first end and a second end and having a plurality of gear teeth (126) at a radially outer surface adjacent the first end, and the gear teeth (126) having a gear tooth profile, with roll angles A, B, C, and D, and the roll angle at A being between 17.0 and 18.5°, the roll angle at B being between 20.0 and 21.5°, the roll angle at C being between 29.5 and 31.0°, and the roll angle at D being between 32.5 and 34.0°. In addition, an integrated drive generator is disclosed as is a method of replacing an accessory drive gear in an integrated drive generator.