Patent Application
20150122941
The subject matter disclosed herein relates to the art of rotary wing aircraft and, more specifically, to coaxial multi-rotor systems for rotary wing aircraft.
In typical rotary winged aircraft, for example, helicopters with dual coaxial rotor systems, or upper rotor assemblies and lower rotor assemblies, the systems typically include several sets of bearings between the upper rotor shaft and lower rotor shaft to transfer loads between the shafts. The bearings and controls for the upper rotor assembly drive an increased diameter for the upper rotor shaft, and thus the lower rotor shaft, which increases drag during operation. As such, many coaxial rotor systems include an aerodynamic fairing positioned between the upper rotor assembly and the lower rotor assembly for drag reduction and to improve operational characteristics of the helicopter. The fairing is typically directional, meaning that for optimal performance it has a specific alignment with the fuselage of the helicopter. Mounting the fairing between the upper rotor assembly and the lower rotor assembly and maintaining this preferred alignment is difficult due to rotation of the shaft between the rotor assemblies. Typically, the installation includes mounting the fairing to the rotating shaft and providing a number of powered motors or actuators to counterrotate the fairing with respect to the shaft to maintain the preferred alignment with the fuselage.
In one embodiment, a coaxial, dual rotor system for an aircraft includes a first rotor assembly located at a rotor axis and a second rotor assembly located at the rotor axis. An aerodynamic fairing is positioned between the first rotor assembly and the second rotor assembly along the rotor axis. A planetary gear arrangement is operably connected to the fairing and operably connected to an airframe of the aircraft to maintain a selected rotational orientation of the fairing about the rotor axis relative to the airframe.
In another embodiment, a dual coaxial rotor rotorcraft includes an airframe, a drive system disposed at the airframe, and a coaxial, dual rotor system operably connected to the drive system. The rotor system includes a first rotor assembly located at a rotor axis and a second rotor assembly located at the rotor axis. An aerodynamic fairing is positioned between the first rotor assembly and the second rotor assembly along the rotor axis. A planetary gear arrangement is operably connected to the fairing and operably connected to the airframe of the rotorcraft to maintain a selected rotational orientation of the fairing about the rotor axis relative to the airframe.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Shown in
Referring to
The attachment of the fairing 48 and the positioning thereof is described in more detail with reference to
A planet carrier 56 is attached to the lower rotor shaft 44 and extends radially outwardly from the lower rotor hub 38 between adjacent rotor blades 36. Alternatively, in other embodiments, the planet carrier 56 extends through rotor blades 36 of the lower rotor assembly 32 or is formed unitary with the rotor blades 36. An upper planet gear 58 and lower planet gear 60 are secured to a planet shaft 62 extending through the planet carrier 56 and rotate synchronously. The upper planet gear 58 meshes with the upper sun gear 52, while the lower planet gear 60 meshes with the lower sun gear 50. In some embodiments, a single planet carrier 56 and accompanying upper planet gear 58 and lower planet gear 60 are utilized, while in other embodiments, multiple such assemblies, such as 2, 3 or 5 planet carriers 56 and accompanying upper planet gear 58 and lower planet gear 60 are utilized to balance the assembly. Through this arrangement, as the lower rotor hub 38 rotates, the fairing 48 secured to the upper sun gear 52 maintains rotational alignment with the lower sun gear 50 and the airframe 12. The planetary gear arrangement disclosed herein uses a simple, nonpowered structure that passively maintains the selected alignment of the fairing 48 and the airframe 12.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. For instance, aspects can be used with propeller assemblies, turbines, and/or fans. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
