Sun Gear Differential for Integrated Drive Generator Packaging
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Solution Overview
Problem
The two ring gear configuration in aircraft electric power generation hydro-mechanical transmissions is limited to a lower input speed range and forces specific packaging arrangements, requiring side-to-side placement with a hydraulic unit and additional gearing, which restricts flexibility and efficiency.
Innovation Solution
A sun gear configuration for an integrated drive generator with a differential that allows for a wider input speed range and enables coaxial packaging with the hydraulic unit, eliminating the need for gearing between the sun gear and hydraulic unit, using a back-to-back axial piston pump to actively control the sun gear speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two ring gear configuration is used in the differential, then the differential can be constructed with standard planet gears, but the input speed range is limited to lower speeds and packaging flexibility is restricted
Solution Approach 1:
The patent applies asymmetry by introducing a sun gear to create an asymmetric planetary gear arrangement. The differential now includes a sun gear, planet gears, and a single ring gear instead of two symmetric ring gears. This asymmetric configuration enables a variable differential ratio that can accommodate a broader input speed range while maintaining constructability with standard gear components.
Solution Approach 2:
The patent changes the fundamental parameter of differential ratio from a fixed value (1:1 in two ring gear config) to a variable parameter controlled by sun gear positioning. By actively controlling the sun gear's rotational speed and position, the differential ratio becomes adjustable, allowing the system to adapt to different input speed ranges and improve overall system versatility.
2Ease of operation
If a two ring gear configuration is used, then the differential structure is established, but specific packaging arrangements are forced requiring side-to-side placement with hydraulic unit and additional gearing
Solution Approach 1:
The patent merges the differential and hydraulic unit into a coaxial arrangement, eliminating the need for separate side-to-side placement and additional intermediary gearing. The sun gear configuration allows the hydraulic unit to be positioned along the same axis as the differential, simplifying the overall packaging and reducing the number of required components.
Solution Approach 2:
The patent transitions from a side-to-side (lateral) packaging arrangement to a coaxial (longitudinal) packaging arrangement. This dimensional change in the spatial configuration allows the hydraulic unit and differential to share the same axis, improving packaging flexibility and eliminating the need for additional gearing mechanisms.
3Speed
If additional gearing is included between differential and hydraulic unit to accommodate two ring gear configuration, then speed conversion is achieved, but device size and complexity increase
Solution Approach 1:
The patent extracts and eliminates the unnecessary intermediary gearing from the system. By using the sun gear configuration, the speed conversion function is achieved directly through the planetary gear mechanism itself, removing the need for additional separate gearing components and reducing the overall device volume.
Data Source
AI summary
Embodiments herein relate to piece-part, sub-assembly, assembly, and component levels of a differential composed of a sun gear configuration and utilized in an integrated drive generator. An integrated drive generator is a hydro-mechanical transmission that drives a synchronous salient pole generator. The integrated drive generator is a constant speed output, variable speed input transmission that includes the differential and a hydraulic unit. In general, the integrated drive generator utilizes the variable speed input from an accessory gear box of an engine to drive or control a hydraulic unit, which in turn drives or controls a churn leg member of the differential. As the differential is driven, speeds of each speed member of the differential are then summed to generate the constant speed output to drive the synchronous salient pole generator.