Aircraft Rotor Epicyclic Gear Transmission for Accessory Speed
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Solution Overview
Problem
Existing helicopter rotors face challenges in driving accessory components at a second rotational speed different from the main rotor's speed without increasing size or weight, and existing solutions require substantial redesign or complex tuning of counter-rotating masses.
Innovation Solution
The implementation of an epicyclic gear train and an electrical generator within the rotor, utilizing a differential rotational speed between the mast and hub to induce an electromotive force, allowing for the efficient operation of accessory components like vibration dampers and de-icing systems without altering the rotor's size or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If accessory components are driven at a different rotational speed using traditional transmission methods, then the rotational speed requirement is met, but the rotor size and weight increase substantially
Solution Approach 1:
The patent implements an epicyclic gear train where the sun gear is mounted on the mast, planet gears are positioned around it, and the ring gear is integrated with the hub. This nested arrangement allows multiple gear elements to occupy overlapping spatial volumes, achieving high transmission ratios without increasing the overall rotor diameter or weight significantly.
Solution Approach 2:
The epicyclic gear train utilizes three-dimensional spatial arrangement by positioning planet gears on radial arms that rotate around the sun gear axis. This transforms a simple linear transmission into a multi-dimensional gear system where motion occurs in both radial and axial directions, enabling compact high-ratio transmission within the existing rotor envelope.
2Speed
If accessory components are driven at a different rotational speed using traditional transmission methods, then the rotational speed requirement is met, but the rotor size increases
Solution Approach 1:
The epicyclic gear train elements (sun gear, planet gears, ring gear) are nested within the existing mast and hub structure. The planet gears rotate around the sun gear while being contained within the hub's internal volume, allowing the transmission system to fit within the existing rotor footprint without increasing its external dimensions.
Solution Approach 2:
The epicyclic gear train serves multiple functions simultaneously: it provides the required speed reduction for accessory components, transmits power from the mast to the hub, and maintains the structural integrity of the rotor assembly. This multi-functionality eliminates the need for separate transmission components that would increase volume.
3Object-affected harmful factors
If counter-rotating masses are used for vibration damping, then vibration control is achieved, but the device complexity increases due to tuning requirements
Solution Approach 1:
The vibration damping function is merged with the existing epicyclic gear train structure. Counter-rotating masses are integrated into the planet gear carrier or ring gear assembly, allowing the same structural elements to provide both power transmission and vibration damping functions. This eliminates the need for separate vibration damper components and their associated tuning mechanisms.
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 solution enables the efficient operation of accessory components at a different rotational speed without increasing the rotor's size or weight, providing a high transmission ratio in a compact design that can be easily integrated into existing rotors, supporting both anti-icing and active aerodynamic control functions.
Implementation Method 1
an epicyclic gear train (17), which transmits the motion from an end shaft (not shown) of main transmission group (7) to mast (11) and hub (12)
Implementation Method 2
The rotor (3) further comprises an electrical generator, which comprises a source (30) of magnetic field, which is driven in rotation about axis A with a first rotational speed (ω1), and an electric conductive element (32), which is operatively connected to mast (11) and is driven in rotation at a second rotational speed (ω2) different from first rotational speed (ω1), wherein electric conductive element (32) is electromagnetically coupled with source (30) so that an electromotive force is magnetically induced, in use, in electric conductive element (32) itself
Data Source
AI summary
A rotor for an aircraft capable of hovering includes a stationary support structure and a rotative element, which is rotatable about a first axis with respect to said stationary support structure with a first rotational speed. The rotor includes at least one blade, which is operatively connected with said rotative element; and a transmission group, which includes an output element rotatable about first axis with a second rotational speed different from first rotational speed.