Output Ring Gear Tooth Profile for Constant Generator Speed
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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 performance of the output ring gear and accessory systems like scavenge and charge pumps.
Innovation Solution
The output ring gear design features a gear body with specific roll angles for outer and inner gear teeth, allowing for efficient rotational input to the generator and accessory drive gear, ensuring consistent power frequency by optimizing the gear tooth profiles and angles.
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 profile adjustable through a trimming unit. The ring gear can be dynamically reconfigured with different tooth profiles (varying roll angles) to adapt to different engine speeds while maintaining constant output frequency. This is achieved through a mechanism that allows the ring gear teeth to be positioned at different angles relative to the planet gears, enabling the system to optimize performance across varying input speeds.
2Reliability
If a speed trimming hydraulic unit is added to maintain constant output speed, then the power frequency can be stabilized, but the device complexity increases
Solution Approach 1:
The patent merges the speed trimming function directly into the ring gear structure itself. Instead of adding a separate hydraulic trimming unit as a distinct subsystem, the trimming capability is integrated into the ring gear's tooth profile design. The ring gear incorporates adjustable tooth angles that can be trimmed to different configurations, combining the gear transmission and speed control functions into a single integrated component, thereby reducing overall system complexity.
3Productivity
If the ring gear is designed with specific roll angles for gear teeth, then the power transmission efficiency is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by providing specific roll angle ranges for the gear teeth rather than fixed precise values. The outer gear teeth have roll angles of 17.3-18.8° at point A, 18.3-19.8° at point B, 21.3-22.8° at point C, and 22.2-23.7° at point D. The inner gear teeth have roll angles of 31.6-33.1° at point A, 30.0-31.5° at point B, 25.4-26.9° at point C, and 23.9-25.4° at point D. These ranges allow for manufacturing tolerances while optimizing power transmission efficiency.
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
An output ring gear (40) for use in an integrated drive generator has a gear body (120) extending between a first end (122) and a second end (124) and having a disc (126) extending radially outwardly. A boss (127) extends from the disc (126) toward the second end (124). There are outer gear teeth (128) outwardly of an outer diameter of the disc (126). There are inner gear teeth (130) inwardly of an inner surface of the disc (126). The outer and inner gear teeth (128,130) have a unique gear tooth profile with roll angles A, B, C, and D. An integrated drive generator (20) and a method are also disclosed.