Abstract:
An upper rotor control system is contained within an upper rotor shaft and upper hub assembly of a contra-rotating rigid rotor system. A collective servo assembly includes a hydraulic actuator that provides collective pitch to all blades through axial extension/retraction of the control rod relative the upper rotor shaft for collective pitch control of the rotor blades. The collective servo assembly includes a spherical bearing for attachment of the control rod to aircraft structure. An X-Y positioner assembly includes a bearing arrangement which allows the shaft to rotate, while the X-Y positioner assembly remains non-rotational therein. The X-Y positioner assembly includes a multitude of hydraulic actuators, orthogonally positioned, to tilt the control rod about the spherical bearing off the axis of rotation of the upper rotor shaft for cyclic pitch control of the rotor blades.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a rotor control system for a rotary-wing aircraft, and more particularly to an upper rotor control system for a counter-rotating rotor system. 
         [0002]    Control of a rotary-wing aircraft is affected by varying the pitch of the rotor blades individually as the rotor rotates and by varying the pitch of all of the blades together. These are known respectively as cyclic and collective pitch control. Blade pitch control of a rotary wing aircraft main rotor is typically achieved through a swashplate assembly which transfers the motion of non-rotating control members to the rotating members. 
         [0003]    The swash plate assembly is typically concentrically mounted about a rotor shaft. The swash plate assembly generally includes two rings connected by a series of bearings with one ring connected to the airframe (stationary), and the other ring connected to the rotor hub (rotating). The rotating ring is connected to the rotor hub through a pivoted link device typically referred to as “scissors”, with the static ring similarly connected to the airframe. The rotating swash plate rotates relative the stationary swash plate. Apart from rotary motion, the stationary and rotating swash plate otherwise move as a unitary component. 
         [0004]    Collective control is achieved by translating the swash plate assembly up and down with respect to the rotor shaft and cyclic control is achieved by tilting the swash plate relative to the rotor shaft. The stationary ring is typically mounted about the rotor shaft through a spherical ball joint or uniball that allows for tilt of the swash plate assembly, with the standpipe surrounding the rotor shaft allowing translation of the swash plate assembly along the axis. The pitch links connect the rotating ring of the swash plate assembly to the pitch or control arms of the rotor blades. The stationary swash plate assembly of the swash plate assembly is positioned by servos which are actuated in response to the pilot&#39;s control signals. Thus, when the pilot inputs a control command, the stationary swash plate assembly is raised, lowered or tilted and the rotating swash plate assembly follows to impact collective and cyclic pitch control to the rotor disc. 
         [0005]    A rotary wing aircraft with a counter-rotating rotor system requires an upper and lower rotor control system. Modern flight control systems may also control the upper rotor system independent of the lower control system so as to provide increased fidelity of aircraft control. The lower rotor system typically utilizes a relatively conventional swashplate arrangement mounted about a lower rotor shaft while the upper rotor system utilizes a relatively more complex upper rotor control system mounted through the upper rotor shaft which counter-rotates relative the lower rotor shaft. The upper rotor control system includes an upper rotor swashplate assembly, a motion multiplier, and long control rods, located inside the upper rotor shaft. Buckling stability of the long rods requires a relatively heavy, large diameter solution which may be difficult to package within the rotor shaft. 
         [0006]    Accordingly, it is desirable to provide a compact, light-weight upper rotor control system for a counter-rotating rigid rotor system. 
       SUMMARY OF THE INVENTION 
       [0007]    The upper rotor control system for a counter-rotating rotor system according to the present invention generally is contained within an upper rotor shaft of the counter-rotating shafts. The upper rotor control system generally includes a collective servo assembly, a control rod, an X-Y positioner assembly, a duplex bearing control rod linkage, a pitch beam, a pitch beam uniball and a pitch beam hub support. 
         [0008]    The collective servo assembly includes a hydraulic actuator that provides collective pitch to all blades through axial movement of the control rod relative the rotor shaft. The collective servo assembly includes a spherical bearing for attachment of the control rod to fixed (non-rotating) aircraft structure about which the control rod tilts. 
         [0009]    The X-Y positioner assembly includes a bearing arrangement which allows the shaft to rotate, while the X-Y positioner assembly and control rod remain non-rotational therein. The X-Y positioner assembly includes a multitude of hydraulic actuators, orthogonally positioned adjacent the upper end of the control rod opposite the collective servo assembly to tilt the control rod off the axis of rotation of the upper rotor shaft for cyclic control of the rotor blades. 
         [0010]    The duplex bearing control rod linkage includes a uniball linkage attachment between the control rod and a rotational bearing arrangement mounted to the pitch beam such that the pitch beam rotates relative the control rod upon the bearing arrangement while cyclic pitch movement between the pitch beam and the control rod is accommodated by the uniball linkage. 
         [0011]    The pitch beam is supported within the hub assembly through the pitch beam uniball upon the pitch beam hub support which projects from an upper hub surface of the hub assembly. The pitch beam uniball slides along the pitch beam hub support during axial movement (collective) of the pitch beam and tilts about the uniball during tilting movement (cyclic). A pitch beam scissor assembly attaches between the pitch beam and the hub assembly to accommodate axial (collective) and tilting (cyclic) motions of the pitch beam. 
         [0012]    The present invention therefore provides a compact, light-weight upper rotor control system for a counter-rotating rotor system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0013]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
           [0014]      FIG. 1  is a general perspective side view of an exemplary rotary-wing aircraft embodiment for use with the present invention; 
           [0015]      FIG. 2  is an expanded partial phantom view of a dual, counter-rotating, coaxial rotor system of the aircraft of  FIG. 1 ; 
           [0016]      FIG. 3  is a partial fragmentary view of the a dual, counter-rotating, coaxial rotor system; 
           [0017]      FIG. 4  is a partial fragmentary view of the upper rotor system of the dual, counter-rotating, coaxial rotor system; 
           [0018]      FIG. 5A  is a perspective partial phantom view of an X-Y positioner assembly of the upper rotor control system; 
           [0019]      FIG. 5B  is a top sectional view of the X-Y positioner assembly; 
           [0020]      FIG. 6  is a perspective view of the upper rotor control system; 
           [0021]      FIG. 7  is a top perspective view of a pitch beam of the upper rotor control system connected to a pitch link of the rotor blades; 
           [0022]      FIG. 8A  is a side partial fragmentary view of the pitch beam of the upper rotor control system; 
           [0023]      FIG. 8B  is a schematic view of the pitch beam uniball and pitch beam hub support for the pitch beam of the upper rotor control system; and 
           [0024]      FIG. 8C  is a side partial fragmentary view of the pitch beam of the upper rotor control system in a pitched position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]      FIG. 1  illustrates an exemplary vertical takeoff and landing (VTOL) rotary-wing aircraft  10  having a dual, counter-rotating, coaxial rotor system  12  which rotates about an axis of rotation A. The aircraft  10  includes an airframe  14  which supports the dual, counter rotating, coaxial rotor system  12  as well as an optional translational thrust system T which provides translational thrust generally parallel to an aircraft longitudinal axis L. Although a particular aircraft configuration is illustrated in the disclosed embodiment, other counter-rotating, coaxial rotor systems will also benefit from the present invention. 
         [0026]    A main gearbox  26  which may be located above the aircraft cabin drives the rotor system  12 . The translational thrust system T may be driven by the same main gearbox  26  which drives the rotor system  12 . The main gearbox  26  is driven by one or more engines (illustrated schematically at E). As shown, the main gearbox  26  may be interposed between the gas turbine engines E, the rotor system  12  and the translational thrust system T. 
         [0027]    Referring to  FIG. 2 , the dual, counter-rotating, coaxial rotor system  12  includes an upper rotor system  16  and a lower rotor system  18 . Each rotor system  16 ,  18  includes a plurality of rotor blade assemblies  20  mounted to a rotor hub assembly  22 ,  24  for rotation about the rotor axis of rotation A. The plurality of the main rotor blade assemblies  20  project substantially radially outward from the hub assemblies  22 ,  24 . Any number of main rotor blade assemblies  20  may be used with the rotor system  12 . 
         [0028]    The rotor system  12  preferably also includes a rotor hub fairing system Fh generally located between and around the upper and lower rotor systems  16 ,  18  such that the rotor hub assemblies  22 ,  24  are at least partially contained therein. The rotor hub fairing system Fh preferably includes an upper hub fairing Fu, a lower hub fairing Fl and a shaft fairing Fs therebetween. The shaft fairing Fs is preferably attached to the counter-rotating, coaxial rotor system  12  through a bearing arrangement Bu, Bl such that the shaft fairing Fs is aligned with the relative wind in forward flight but may alternatively be free to pivot during low speed maneuvering. The upper bearing Bu and the lower bearing Bl are respectively located adjacent an upper portion and a lower portion of the shaft fairing Fs. The upper bearing Bu is preferably attached to one rotor shaft  12 U while the lower bearing Bl attached to the other rotor shaft  12 L such that the bearings are counter rotating and net bearing drag is relatively low. 
         [0029]    Referring to  FIG. 3 , each rotor blade assembly  20  of the rotor system  12  generally includes a rotor blade  28  (illustrated somewhat schematically),;a rotor blade spindle  30 , and a rotor blade bearing  32  which supports the rotor blade spindle  30  within a bearing housing  34 . It should be understood that various blade attachments may also be utilized with the present invention. 
         [0030]    A lower rotor control system  36  includes a rotor blade pitch control horn  38  mounted for rotation with the rotor blade spindle  30  of each rotor blade  28 . Each rotor blade pitch control horn  38  is linked to a lower swashplate  40  ( FIG. 2 ) through a pitch control rod  41  to impart the desired pitch control thereto. It should be understood that the pitch control rods  41  for the lower rotor system  18  are preferably located external to the main rotor shaft  12 L for pitch control of the lower rotor system  18 . It should be understood, that various pitch control rods and links at various locations for cyclic and collective pitch control of the lower rotor system  18  may be utilized with the present invention. It should be further understood that control of the lower rotor system  18  may be of conventional design such that it need not be described in particular detail herein. 
         [0031]    Referring to  FIG. 4 , the upper rotor control system  42  is preferably contained within the upper rotor shaft  12 U which counter-rotates relative the lower rotor shaft  12 L. The upper rotor control system  42  generally includes a collective servo assembly  50 , a control rod  52 , an X-Y positioner assembly  54 , a duplex bearing control rod linkage  56 , a pitch beam  58 , a pitch beam uniball  60  and a pitch beam hub support  62 . The control tube  52  preferably provides a geometry conducive to manufacture in composites (such as carbon fiber in resin) to minimize component weight. 
         [0032]    The collective servo assembly  50  includes a spherical bearing  64  which attaches a collective servo  66  mounted to fixed aircraft structure (illustrated schematically). The spherical bearing  64  defines the point at which the control rod  52  tilts about. It should be understood that other mounting arrangements may likewise be utilized to define this point. The control rod  52  is attached to the collective servo  50  within a control rod sleeve  68  or the like to further support the control rod during axial (collective) movement along axis A. Preferably, the control rod sleeve  68  contains a collective hydraulic cylinder, rigidly attached at its upper end to the control rod  52  to provide an essentially pinned/pinned beam that can vary axially in length. 
         [0033]    Referring to  FIG. 5A , the X-Y positioner  54  assembly enables the control rod  52  to be tilted in an X-Y direction about the spherical bearing  64  where Z is defined along the axis of rotation A while accommodating axial movement (collective). The X-Y positioner assembly  54  generally includes a support sleeve  70  mounted within the rotor shaft  12 U upon a bearing assembly  74  which is preferably a needle bearing arrangement. The support sleeve  70  supports an outer race  72  for axial movement relative thereto. The outer race  72  includes a cylindrical outer diameter  76 C and a spherical inner diameter  76 S within which a spherical inner member  78  of the uniball is mounted. 
         [0034]    Preferably, a low friction interface  80  such as a Teflon interface surface or the like between the cylindrical outer diameter  76 C and the support sleeve  70  facilitates movement therebetween such that the axial movement (collective) of the control rod  52  is accommodated thereby. Preferably, scissor arrangements  82 A,  82 B (illustrated schematically) are arranged between the spherical inner member  78  and the support sleeve  70  and the outer race  72  respectively to prevent the support sleeve  70  and outer race  72  from rotating relative the shaft  12 U while accommodating relative vertical and tilt movements therebetween. It should be understood that other anti-rotation systems may alternative or additionally be provided. 
         [0035]    The spherical inner member  78  of the uniball is movable within the outer race  72  of the uniball to accommodate control rod  52  tilt off axis A. The spherical inner member  78  of the uniball supports two sets of orthogonal actuators  84 A,  84 B and  86 A,  86 B such as hydraulic cylinders with the cylinders fixed to the control rod  52 . The two sets of orthogonal actuators  84 A,  84 B and  86 A,  86 B are fixed within the control rod  52  such that operation of the orthogonal actuators  84 A,  84 B and  86 A,  86 B tilts the control rod  52  off axis A. That is, the set of orthogonal actuators  84 A,  84 B tilt the control rod in the X-axis while the set of orthogonal actuators  86 A,  86 B tilt the control rid  52  in the Y-axis. More than a single actuator is preferably provided in each set so as to provide redundant operation in each of the X and Y axes. 
         [0036]    Referring to  FIG. 5B , each set of orthogonal actuators  84 A,  84 B and  86 A,  86 B are attached to a set of slides  88 A,  88 B and  90 A,  90 B which are each engaged within a respective groove  92 A- 92 D formed within the inner surface of the spherical inner member  78  of the uniball to allow one set  88 A,  88 B or  90 A,  90 B to slide within the associated grooves  92 A- 92 D while the other set  90 A,  90 B or  88 A,  88 B are actuated. Movement of the slides  88 A,  88 B  90 A,  90 B, within grooves  92 A- 92 D tilt the control rod  52  while the spherical inner member  78  of the uniball accommodates the pitching of the orthogonal actuators  84 A,  84 B and  86 A,  86 B that occurs when the control rod  52  tilts relative axis A. 
         [0037]    The spherical inner member  78  of the uniball is restrained from spinning by the slides  88 A,  88 B and  90 A,  90 B of the hydraulic cylinders which are engaged in the grooves  92 A- 92 D. It should be understood that the sets of orthogonal actuators  84 A,  84 B and  86 A,  86 B may be of various types such as mechanical, electric, magnetic electro-mechanical or otherwise. 
         [0038]    Referring to  FIG. 6 , the duplex bearing control rod linkage  56  preferably includes a uniball linkage  96  attachment between the control rod  52  and a rotational bearing arrangement  94  mounted to the pitch beam  58 . That is, the pitch beam  58  rotates about axis A and relative the control rod  52  upon the bearing arrangement  94  while tilting movement (cyclic) between the pitch beam  58  and the control rod  52  is accommodated by the uniball linkage  96 . 
         [0039]    Referring to  FIG. 7 , the pitch beam  58  is connected to each rotor blade spindle  30  through a pitch horn  98 . The interface between each pitch horn  98  and the pitch beam  58  utilizes a slotted degree of freedom therebetween in which a slot  100  in the pitch beam  58  receives a pin  102  of the pitch horn  98  or vice versa. The kinematics of the pitching movement of the pitch beam  58  requires this slotted degree of freedom to provide transverse movement relative the axis A. The slotted degree of freedom is preferably further facilitated with a resilient interface having spherical and flat pad elastomerics, fabric lined bearings or the like. 
         [0040]    Referring to  FIG. 8A , the pitch beam  58  is mounted within the hub assembly  22  through the pitch beam uniball  60  mounted upon the pitch beam hub support  62 . The pitch beam hub support  62  projects from an upper hub surface  104  of the hub assembly such that the pitch beam uniball  60  slides along the pitch beam hub support  62  during axial movement (collective) of the pitch beam  58  and tilts about the pitch beam uniball  60  during cyclic movement of the pitch beam  58  ( FIG. 8B ). A pitch beam scissor assembly  106  (illustrated somewhat schematically) attaches between the pitch beam  58  and the rotor hub assembly  22  to accommodate vertical (collective) and tilting (cyclic) motions of the pitch beam  58  relative the hub support  62  ( FIG. 8C ). 
         [0041]    It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting. 
         [0042]    Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention. 
         [0043]    The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.