Patent Publication Number: US-2020283139-A1

Title: Hybrid rotor propulsion for rotor aircraft

Description:
TECHNICAL FIELD 
     This disclosure relates in general to the field of aircraft, and more particularly, to a hybrid aircraft rotor propulsion system. 
     BACKGROUND 
     This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
     Conventionally powered rotorcraft, such as helicopters and tiltrotors, are driven by a combustion engine mechanically transmitting power to the rotors. In some rotorcraft, the rotor&#39;s mechanical drive system is replaced with direct drive electric motor systems. In hybrid rotorcraft designs, a combustion engine may drive a main rotor while a separate electric system is used to drive one or more anti-torque rotors. This approach can be used to improve rotorcraft propulsion systems, for example, to reduce noise, reduce weight, or to improve safety. 
     SUMMARY 
     An exemplary aircraft rotor propulsion system includes a motor having a rotational output connected to a rotor and a prime mover connected to the motor through a rotational input, the prime mover configured to apply a rotational input speed to the motor. 
     An exemplary method of controlling a rotational speed of an aircraft rotor includes applying a rotational input speed from a prime mover to a motor and applying a rotational output speed from the motor to the aircraft rotor. 
     Another exemplary method of controlling a rotational speed of an aircraft rotor includes applying, from a prime mover, a rotational input speed through a drive shaft to a motor and applying a rotational output speed to an anti-torque rotor through the motor. 
     This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  illustrates an exemplary aircraft implementing an exemplary hybrid tail rotor propulsion system according to one or more aspects of the disclosure. 
         FIG. 2  illustrates an exemplary aircraft implementing another exemplary hybrid tail rotor propulsion system according to one or more aspects of the disclosure. 
         FIG. 3  illustrates an aircraft rotor implementing an exemplary hybrid aircraft rotor propulsion system. 
         FIG. 4  illustrates another aircraft rotor implementing an exemplary hybrid propulsion system. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various illustrative embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. For example, a figure may illustrate an exemplary embodiment with multiple features or combinations of features that are not required in one or more other embodiments and thus a figure may disclose one or more embodiments that have fewer features or a different combination of features than the illustrated embodiment. Embodiments may include some but not all the features illustrated in a figure and some embodiments may combine features illustrated in one figure with features illustrated in another figure. Therefore, combinations of features disclosed in the following detailed description may not be necessary to practice the teachings in the broadest sense and are instead merely to describe particularly representative examples. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not itself dictate a relationship between the various embodiments and/or configurations discussed. 
       FIG. 1  illustrates an exemplary vertical takeoff and landing (VTOL) rotary aircraft  10  incorporating an exemplary hybrid mechanical-electric tail rotor propulsion system  5 . Aircraft  10  includes a rotor system  12 , a fuselage  14 , and a tail boom  16  carrying an anti-torque system represented by rotor  18  and shroud  7 . Rotor system  12  includes rotor  20  having multiple blades for creating flight. Rotor system  12  may include a control system for selectively controlling the pitch of each blade of rotor  20  to control direction, thrust, and lift of aircraft  10 . Tail boom  16  may include one or more rotors  18 . Rotor  18  generally provides thrust to counter the torque due to the rotation of rotor  20 . In an exemplary embodiment, the pitch of rotor  18  is fixed. Teachings of certain embodiments recognize that rotor  18  may represent one example of a rotor or anti-torque rotor; other examples include, but are not limited to, tail propellers, ducted tail rotors, and ducted fans mounted inside and/or outside the aircraft. The anti-torque system may include two or more rotors  18 , with or without a shroud, such as in a distributed anti-torque system. Teachings of certain embodiments relating to rotors and rotor systems may apply to rotor system  12  and other rotor systems, such as distributed rotors, tiltrotor, tilt-wing, and helicopter rotor systems. It should be appreciated that teachings herein apply to manned and unmanned vehicles and aircraft including without limitation airplanes, rotorcraft, hovercraft, helicopters, and rotary-wing vehicles. 
     Aircraft  10  includes a prime mover  22  mechanically connected to a transmission  24  and transmission  24  is mechanically connected to rotor  20  through mast  26 . Prime mover  22  may be a combustion engine or an electric motor. In this example, tail rotor  18  is a hybrid propulsion driven rotor operationally connected to prime mover  22  and a motor  28 . Motor  28  may be an electric, hydraulic or pneumatic motor. Motor  28  is an electric motor in  FIG. 1 . In an exemplary embodiment, prime mover  22  an electric motor  22  positioned proximate the center of gravity of aircraft  10  and motor  28  is an additional electric motor. 
     Prime mover  22  is mechanically connected to a housing or base of motor  28  via a rotational input, e.g., drive shaft  30 , to provide a rotational input speed to the housing or base of motor  28  and motor  28  provides further rotational output to rotor  18 . In an exemplary embodiment, an electrically driven shaft of motor  28  is connected to tail rotor  18 , whereby motor  28  can change the tail rotor speed relative to the rotational input speed from prime mover  22 . As an electric drive riding on a mechanical drive, typical low power demand flight conditions can result in a generator state for electric motor  28 . The hybrid rotor propulsion system is described herein with reference to an anti-torque tail rotor for the purpose of illustration and with the understanding that the hybrid rotor propulsion system can be utilized with other aircraft rotors, including without limitation main rotors. 
     Motor  28  is operationally connected to a power source  32 , e.g. batteries, and a controller  34 . Electric motor  28  may be controlled by controller  34  over a range of speeds in response to a pilot and/or flight control system. Controller  34  can include logic to control the rate of rotation of rotor  18  via electric motor  28 . Controller  34  may be included for example in the motor controller or the flight computer, be a component of the motor controller or the flight computer, and/or be in communication with the motor controller or the flight computer. 
       FIG. 2  illustrates another exemplary vertical takeoff and landing (VTOL) rotary aircraft  10  incorporating a hybrid rotor propulsion system  5 . In this example, motor  28  is a hydraulic motor that may be driven by a hydraulic pump  32 . Prime mover  22  may be a combustion engine or an electric motor. 
       FIG. 3  illustrates an exemplary aircraft tail rotor  300  implementing an exemplary hybrid rotor propulsion system  302 . Aircraft tail rotor  300  includes one or more blades  304  within a shroud  309 . Rotor  300 , e.g., blades  304 , is operationally connected to a prime mover  306  and a motor  308 . Prime mover  306  may be for example a combustion engine or an electric motor and motor  308  may be an electric, hydraulic, or pneumatic motor. Prime mover  306  is operationally connected through a rotational input, e.g., drive shaft  310 , to motor  308  and motor  308  is operationally connected through a rotational output to rotor  300 . The rotational input may be connected for example to a motor housing, motor base, or motor shaft and the rotor may be connected to one of the other of the motor housing, the motor base, or the motor shaft. 
       FIG. 4  illustrates another exemplary aircraft rotor  400  utilizing a hybrid rotor propulsion system  402 . Aircraft rotor  400  includes one or more blades  404 , for example within shroud  409 . Rotor  400 , e.g., blades  404 , are operationally connected to a prime mover  406 , e.g., a combustion engine or electric motor, and a motor  408 , e.g., electric, hydraulic or pneumatic motor. Prime mover  406  is connected to motor  408  through a rotation input. In  FIG. 4 , prime mover  406  is operationally connected to rotor  400  via drive shaft  410  and gears  403 , e.g., bevel gears. Prime mover  406  provides rotational mechanical shaft power to drive shaft  410  and gears  403  to supply a rotational input speed to motor  408 . 
     A power source  412 , e.g., battery, generator, or hydraulic pump, is operationally connected to motor  408  via a line  414  and a slip ring  416 . A portion, e.g., rotor or stator, of motor  408  is connected to the rotational input from prime mover  406  and the other portion, e.g., stator or rotor, of motor  408  is connected as the rotational output to rotor  400 . For example, in  FIG. 4  motor housing or base  401  is fixed to drive shaft  410 , for example through gears  403  and rotates with drive shaft  410  and gears  403  and a motor drive shaft is fixedly connected to rotor  400 . In some embodiments, the rotational input is fixedly connected to motor shaft  405  and housing or base  401  is fixedly connected to rotor  400 . 
     Rotational input speed is applied from prime mover  406  through drive shaft  410  to base  401  of motor  408  and a rotational output speed is applied from motor drive shaft  405  to rotor  400 , i.e., rotor blades  404 . The rotational output speed includes a speed of zero RPMs. 
     In an exemplary embodiment, input drive shaft  410  is connected to base  401  (rotor or stator) of motor  408  via bevel gear  403 , to drive motor  408  at 100 percent of the rotational input speed (RPM) of bevel gear  403 . If 100 percent rotor speed is desired, for example for anti-torque thrust, motor  408  remains magnetically locked and no additional power is supplied to motor  408  and motor  408  does not supply additional rotational speed to rotor  400 . If rotational speed is needed in excess of the 100 percent input speed provided by drive shaft  410 , motor  408  is powered to apply rotational speed in the same direction as bevel gear  403  resulting in higher rotor speed than the input rotational speed at bevel gear  403 . Additional power may be desired, for example for an anti-torque rotor, during sideward flight conditions. If rotor  400  needs less than 100 percent of the input rotational speed, for example during forward cruise flight, motor  408  is unlocked allowing slippage and effectively slowing the rotor rotational speed and resulting in electric motor  408  operating as a generator to charge batteries  32  ( FIG. 1 ) and/or to run accessory equipment. 
     Motor  408  can be operated in reverse to reduce rotational speed output through motor shaft  405  to rotor blades  404  relative to the input rotational speed, to stop rotation of rotor blades  404 , or reverse the thrust direction of rotor blades  404 . For example, with reference in particular to anti-torque rotors  400 , it may be desired to reduce or stop rotation of rotor blades  404 , for example to reduce noise during flight, or for safety when on the ground. To reduce the rotational speed of rotor blades  404 , power, e.g., current, hydraulic fluid, supplied to motor  408  may be reduced to a level where the aerodynamic load on rotor blades  404  will drive motor  408  in a reverse direction relative to input drive shaft  410 , thus allowing power to be extracted from motor  408 . Such operation results in a rotor rotational speed less than the rotational speed input by prime mover  406  and drive shaft  410 . To completely stop the rotation of rotor  400 , a low level of power may be applied to motor  408  to drive motor  408  in a reverse direction relative to drive shaft  410  and at a rotational speed equal to the rotational speed of bevel gear  403  as supplied by prime mover  406  and drive shaft  410 . To provide reverse thrust, power is supplied to motor  408  to drive motor  408  at a reverse rotational speed greater than the input rotational speed of bevel gear  403  as driven by drive shaft  410 . 
     An exemplary hybrid aircraft rotor propulsion system combines a combustion engine mechanically connected to rotate a motor housing, and a motor shaft connected to a rotor. The combustion engine applies an approximately constant rotational input speed to the motor housing. By regulating the motor current, the rotor RPM can be precisely controlled, or completely stopped. If the desired rotor RPM is higher than the rotational speed of the mechanically-driven motor housing, then the additional power is supplied by the electric motor. If the desired rotor RPM is less than the rotational speed of the mechanically-driven motor housing, then the motor can be used to generate electrical power. 
     An exemplary method of controlling a rotational speed of an aircraft rotor includes applying a rotational input speed through a drive shaft to a motor and applying a rotational output speed to the aircraft rotor through the motor. This hybrid system provides full rotor RPM control with the majority of the power being supplied by the mechanical drive. The hybrid design eliminates the need for a much heavier, high power electric motor that would otherwise be required to power the rotor if an all-electric direct rotor drive is used. 
     Conditional language used herein, such as, among others, “can,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include such elements or features. 
     In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “inboard,” “outboard,” “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. As used herein, the terms “connect,” “connection,” “connected,” “in connection with,” and “connecting” may be used to mean in direct connection with or in connection with via one or more elements. Similarly, the terms “couple,” “coupling,” and “coupled” may be used to mean directly coupled or coupled via one or more elements. 
     The term “substantially,” “approximately,” and “about” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. The extent to which the description may vary will depend on how great a change can be instituted and still have a person of ordinary skill in the art recognized the modified feature as still having the required characteristics and capabilities of the unmodified feature. In general, but subject to the preceding, a numerical value herein that is modified by a word of approximation such as “substantially,” “approximately,” and “about” may vary from the stated value, for example, by 0.1, 0.5, 1, 2, 3, 4, 5, 10, or 15 percent. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure and that they may make various changes, substitutions, and alterations without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.