Speed control assembly and methods of using same

A speed control assembly includes an input drive shaft coupled to a first gear subassembly having a rotatable gear, a second gear subassembly coupled to an output drive shaft, and a linkage coupling the first and second gear subassemblies, wherein the input drive shaft, the first and second gear subassemblies, and the linkage are configured such that a rotational speed of the rotatable gear adjusts a ratio of a rotational speed of the output drive shaft to a rotational speed of the output drive shaft. In some embodiments, the first gear subassembly includes a sun gear coupled to the input drive shaft, one or more planet gears, and a ring gear as the rotatable gear. In some embodiments, the second gear subassembly includes a sun gear coupled to the output drive shaft, one or more planet gears, and a fixed ring gear.

Not Applicable.

BACKGROUND

The high speeds generated by helicopter tail rotors present hazards to helicopter crews, passengers, and bystanders during routine landing and takeoff, and especially in the course of high-risk applications such as military operations, search and rescue, and emergency medical services. A means for adjusting the speed of a helicopter tail rotor independent of a primary rotor would be beneficial in that the tail rotor could be stopped or reduced to safe speeds when the helicopter is not in flight but while the primary rotor is still engaged. However, countervailing design considerations have resulted in few, if any, helicopters capable of independent adjustment of the tail rotor speed. Thus, there is a continuing need to find new ways by which the rotational speeds of aircraft rotors, propellers, and proprotors can be reduced.

The high speeds of helicopter tail rotors, which may rise to nearly super-sonic levels, are also responsible for producing excess noise. Rotor noise presents a nuisance to the general public in terms of noise pollution as well as a strategic disadvantage during military operations in that the element of surprise may be prematurely compromised, jeopardizing aircraft personnel and mission objectives. Thus, the aviation industry continually seeks new ways by which the rotor noise of rotor-propelled aircraft can be reduced.

Noise issues are further complicated in that the sound produced by helicopter tail rotors changes with altitude because the air thickness decreases and distance from a listener increases at greater elevations. Thus, a need exists to find new ways by which noise from rotary aircraft can be dynamically controlled.

SUMMARY

In some embodiments of the disclosure, a speed control assembly is provided that includes an input drive shaft coupled to a first gear subassembly having a rotatable gear, a second gear subassembly coupled to an output drive shaft, and a linkage coupling the first gear subassembly to the second gear subassembly, wherein the input drive shaft, the first gear subassembly, the second-gear subassembly, and the linkage are configured such that a rotational speed of the rotatable gear adjusts a ratio of a rotational speed of the output drive shaft to a rotational speed of the input drive shaft. In some embodiments, the first gear subassembly may be a first epicyclic or planetary gear subassembly that includes a sun gear coupled to the input drive shaft, one or more planet gears, and the rotatable gear, and wherein the rotatable gear comprises a ring gear of the first epicyclic or planetary gear subassembly. In some embodiments, the second gear subassembly may be a second epicyclic or planetary gear subassembly that includes a sun gear coupled to the output drive shaft, one or more planet gears, and a fixed ring gear. In some embodiments, a counter-rotation device is coupled to the rotatable ring gear and configured to adjust a speed of counter-rotation of the rotatable ring gear relative to the sun gear coupled to the input drive shaft.

In some embodiments of the disclosure, a speed control assembly is provided that includes an input drive shaft coupled to one or more planet gears of a first epicyclic gear subassembly, an output drive shaft coupled to one or more planet gears of a second epicyclic gear subassembly, and a linkage coupling a ring gear of the first epicyclic gear subassembly to a ring gear of the second epicyclic gear subassembly, wherein the one or more planet gears of the first epicyclic gear subassembly are coupled to a rotatable sun gear and to the ring gear of the first epicyclic gear subassembly.

In other embodiments of the disclosure, a method of controlling the speed of an output drive shaft is provided that includes rotating an input drive shaft coupled to a gear subassembly comprising a rotatable ring gear, wherein an output drive shaft is mechanically coupled to the rotatable ring gear, and adjusting a drive speed ratio by controlling a rotational speed of the rotatable ring gear, wherein the drive speed ratio is the ratio of a rotational speed of the output drive shaft to a rotational speed of the input drive shaft. In an embodiment, the rotatable ring rotates in a radial direction opposite to a rotational direction of the input drive shaft.

In an embodiment, the auxiliary rotor of the method of controlling the speed of an auxiliary rotor is a tail rotor of a helicopter and the method further includes adjusting the noise generated by the tail rotor by adjusting the drive speed ratio. In an embodiment, the auxiliary rotor comprises an auxiliary rotor of a vehicle propulsion system and the method of controlling the speed of an auxiliary rotor further includes adjusting the drive speed ratio.

DETAILED DESCRIPTION

As defined herein, the adjective “fixed” indicates that the fixed thing (e.g., a ring gear) does not move (e.g., rotate) relative to a housing or frame supporting the apparatus of which the fixed thing is a component. Unless otherwise specified, use of the terms “connect,” “engage,” “couple,” “attach,” or any other like term describing an interaction between elements is not meant to limit the interaction to direct interaction between the elements and may also include indirect interaction between the elements described. As used herein, the definitions of the terms “speed,” “rotational speed,” “rotation speed,” and “speed of rotation” encompass both the concepts of angular speed (e.g., rotational speed) and rotational direction (e.g., clockwise or counterclockwise), except where context indicates otherwise.

In some cases, it may be desirable to provide a means for controlling the rotational speed of an auxiliary rotor independent of a primary rotor of a propulsion system. In some embodiments, an input shaft is coupled to a first epicyclic or planetary gear subassembly, a second epicyclic or planetary subassembly is coupled an output drive shaft, and a linkage couples the first epicyclic or planetary gear subassembly to the second epicyclic or planetary gear subassembly, wherein a rotatable ring gear of the first epicyclic or planetary gear subassembly may counter-rotate to adjust a ratio of the rotational speed of the output drive shaft to the rotational speed of the input drive shaft, hereinafter referred to as the “drive speed ratio” and represented by the formula ωo:ωi. In some embodiments, the speed control assembly may be coupled to the tail rotor of a helicopter and utilized to maneuver the helicopter, to control noise produced by the tail rotor, or a combination thereof.

FIG. 1is a perspective view of a helicopter1100. Certain embodiments of the disclosure may be used with a helicopter such as helicopter1100. However, it should be understood that the helicopter example is given merely for illustration purposes only. Embodiments of the present disclosure are not limited to any particular setting or application, and embodiments can be used with helicopters, tiltrotor aircraft, airplanes, sea vessels, other types of vehicles, or any other type of rotary shaft.

Helicopter1100includes a main rotor assembly1110, a tail rotor assembly1120, a fuselage1130, and landing gear1140. Main rotor assembly1110includes two or more blades1112that are rotated about an axis of rotation1114in either a clockwise direction or a counterclockwise direction as indicated by arrow1116. Main rotor assembly1110generates a lift force that supports the weight of helicopter1100and a thrust force that counteracts aerodynamic drag. Main rotor assembly1110can also be used to induce pitch and roll of helicopter1100.

Tail rotor assembly1120includes two or more blades1122that are rotated about an axis of rotation1124in either a clockwise direction or a counterclockwise direction as indicated by arrow1126. Tail rotor assembly1120counters the torque effect created by main rotor assembly1110and allows a pilot to control the yaw of helicopter1100.

Fuselage1130is the main body section of helicopter1100. Fuselage1130optionally holds the crew, passengers, and/or cargo and houses the engine, transmission, gear boxes, drive shafts, control systems, etc. that are needed to establish an operable helicopter. Landing gear1140is attached to fuselage1130and supports helicopter1100on the ground and allows it to take off and land.

Speed control assembly1may be situated within the tail portion1131of the fuselage1130. Speed control assembly1allows the speed of rotation around axis of rotation1124of the tail rotor blades1122to be independent of the speed of rotation of blades1112around axis of rotation1114. In various embodiments, the output drive shaft of a speed control assembly of the disclosure may be coupled to an auxiliary rotor of a propulsion system. In some embodiments, the propulsion system may be a propulsion system of a vehicle. The vehicle may be a land vehicle, sea craft, a spacecraft, an aircraft, or any combination thereof. The vehicle may be an aircraft, such as a helicopter, an airplane, a tiltrotor, or other rotary aircraft. The vehicle may be a sea craft such as a boat, a submarine, or a submersible. In an embodiment, the vehicle comprises a helicopter and the auxiliary rotor comprises the tail rotor of a helicopter. The vehicle may be a land vehicle, such as a sport utility vehicle or a car. The vehicle may also be a vehicle capable of traversing two or more terrains such as a hovercraft. The vehicle may be a manned vehicle, an unmanned vehicle (e.g., a drone), or capable of operating in both manned and unmanned capacities. The vehicle may be a remote controllable, autonomous, semi-autonomous, or any combination thereof. The vehicle may also be a hobby vehicle, a toy vehicle, a functional replica, or any combination of any of the vehicles described herein.

Referring now toFIG. 2, an orthogonal right side view of a speed control assembly1in accordance with an embodiment of the disclosure is shown. The speed control assembly1generally comprises an input drive shaft12coupled to a first gear subassembly3, a second gear subassembly5coupled to an output drive shaft18, and a linkage20coupling the first gear subassembly3to the second gear subassembly5. The first gear subassembly3may comprise a rotatable gear, for example a rotatable ring gear34. The second gear subassembly5may comprise a fixed gear, such as a fixed ring gear44. In various embodiments, the location of the rotatable ring gear34and the fixed ring gear44may be reversed such that first gear subassembly3comprises fixed ring gear44and second gear subassembly5comprises rotatable ring gear34. In various embodiments, the first gear subassembly3comprises a first epicyclic or planetary gear subassembly14comprising a sun gear30, planet gears32a,32b,32c, and rotatable ring gear34. In various embodiments, the second gear subassembly5comprises a second epicyclic or planetary gear subassembly24comprising a sun gear40, planet gears42a,42b,42c, and a fixed ring gear44. In various embodiments, the linkage20comprises a first carrier21coupled to each of planet gears32a,32b,32c, a second carrier22coupled to each of planet gears42a,42b,42c, and an intermediate shaft23coupled on opposite ends to each of the carriers21,22. In various embodiments, the speed control assembly1also comprises a rotation speed adjustment device50in contact with a surface of the rotatable gear, such as an outer circumferential surface39of the rotatable ring gear34. The rotation speed adjustment device50may be configured to adjust a rotational speed of the rotatable ring gear34.

Epicyclic or planetary gear subassemblies according to various embodiments of the disclosure may be epicyclic or planetary gear subassemblies. Referring toFIG. 3A, an orthogonal rear view of an epicyclic or planetary gear subassembly64in accordance with an embodiment of the disclosure may generally comprise a sun gear60, one or more planet gears62a,62b,62c, and a ring gear66. The carrier61, other structural features of the speed control assembly, housing containing or providing support for the speed control assembly, or any combination thereof may prevent non-rotational movement of the sun gear60, the one or more planet gears62a,62b,62c, the ring gear66, or any combination thereof. The one or more planet gears62a,62b,62care radially bounded by an outer circumferential surface63of the sun gear and an inner circumferential surface65of the ring gear66. Axial rotation of the sun gear60drives axial rotation of each planet gear62a,62b,62c.

Referring toFIG. 3B, an orthogonal rear view of the epicyclic or planetary gear subassembly ofFIG. 2is shown. The sun gear30, planet gears32a,32b,32c, rotatable ring gear34, or any combination thereof may rotate in a clockwise direction, a counterclockwise direction, or, at different times, in both clockwise and counterclockwise directions. Axial rotation of sun gear30may drive axial rotation of planet gears32a,32b,32cin a direction opposite of sun gear30. The rotatable ring gear34may also rotate in the same direction as sun gear30, in a direction opposite of sun gear30, or, at different times, in both the same and opposite directions of sun gear30. The axial rotation of rotatable ring gear34may drive the axial rotation of planet gears32a,32b,32cin the same rotational direction as rotatable ring gear34. Rotation of rotatable ring gear34may drive planetary rotation of planet gears32a,32b,32cin the opposite rotational direction of rotatable ring gear34. Axial rotation of sun gear30may drive planetary rotation of planet gears32a,32b,32cin the same rotational direction as sun gear30. Simultaneous rotation of sun gear30and rotatable ring gear34may drive rotation of planet gears32a,32b,32cin the same direction, the opposite direction, or, at different times, in both the same and opposite directions as sun gear30, rotatable ring gear34, or a combination thereof. The direction of planetary rotation of planet gears32a,32b,32crelative to each of sun gear30and rotatable ring gear34depends on the ratio of the rotational speed ωsgof sun gear30to the rotational speed ωrrgof the rotatable ring gear34. In an embodiment, the rotatable ring gear34rotates counter to the axial rotation of sun gear30, thereby reducing a speed of planetary rotation ωpgof planet gears32a,32b,32c.

Referring toFIG. 3C, an orthogonal front view of the second epicyclic or planetary gear subassembly24ofFIG. 2is shown. Similar to the first epicyclic or planetary gear subassembly14, sun gear40may rotate clockwise, counterclockwise, or, at different times, both clockwise and counterclockwise. Also similar to the first epicyclic or planetary gear subassembly14, axial rotation of sun gear40drives axial counter-rotation of planet gears42a,42b,42cand planetary rotation of planet gears42a,42b,42cin the same direction as the axial rotation of sun gear40. In an embodiment, ring gear44is fixed in position (e.g., stationary) and thus does not rotate.

Gears of the epicyclic or planetary gear subassemblies may engage each other, other components of the speed control assembly, or a combination thereof via a means for engaging. In some embodiments, the means for engaging comprises interlocking splines, splines67,68a,68b,68c,69shown inFIG. 3Afor example. Examples of suitable splines include but are not limited to parallel key splines, involute splines, crowned splines, serrations, helical splines, and the like. In other embodiments, the gears engage each other, other components of the speed control assembly, or a combination thereof via frictional engagement maintained between the surfaces shared between the gears, other components of the speed control assembly, or a combination thereof. In some embodiments, materials of the circumferential surfaces of the gears, other components of the speed control assembly, of a combination thereof comprise a coefficient of friction that allows for a desired amount of slippage under predetermined conditions. Such slippage may reduce the risk of mechanical failure during operation of the speed control assembly. In other embodiments, the epicyclic or planetary gear subassemblies, components of the speed control assembly, or a combination thereof are engaged with one another via a combination of interlocking splines and frictionally engaged surfaces.

Various epicyclic or planetary gear subassemblies in accordance with embodiments of the disclosure may generally comprise one or more planet gears. The number of planet gears of the first and the second gear sub-assemblies may be the same or different. In an embodiment, each of the first gear subassembly, the second gear subassembly, or both comprise three planet gears. In some embodiments, each of the first gear subassembly, the second gear subassembly, or both comprise fewer (e.g., two) or more (e.g. four or five) planet gears.FIGS. 4A and 4Billustrate simple epicyclic or planetary gear subassemblies comprising three and four planet gears (P) revolving around a single sun gear (S), respectively. In other embodiments, the first gear subassembly, the second gear subassembly, or a combination thereof comprises a compound epicyclic or planetary gear arrangement. The first gear subassembly, the second gear subassembly, or a combination thereof may comprise a meshed-planet epicyclic or planetary gear arrangement, a stepped-planet epicyclic or planetary gear arrangement, a multi-stage epicyclic or planetary gear arrangement, or a combination thereof.

The linkage coupling the first epicyclic or planetary gear subassembly to the second epicyclic or planetary gear subassembly may comprise a linkage that transfers the planetary rotations of planet gears32a,32b,32cto planet gears42a,42b,42c. Referring toFIG. 5A, which shows an orthogonal side view of linkage20ofFIG. 2, some embodiments comprise a first carrier21, a second carrier22, a shaft23coupling the first carrier21and the second carrier22, and shafts71a,71b,71c,81a,81b,81ccoupling each of planet gears32a,32b,32c,42a,42b,42cto the first carrier21and the second carrier22.FIG. 5Bshows an orthogonal side view of a linkage100of speed control assembly160in accordance with an embodiment of the disclosure. The linkage100comprises a carrier101, shafts102a,102b,102c, and shafts103a,103b,103c. Shafts102a,102b,102ccouple each of planet gears104a,104b,104cto carrier101, respectively. Similarly, each of shafts103a,103b,103ccouple planet gears105a,105b,105cto carrier101. Each pair of shafts102a/103a,102b/103b,102c/103cmay comprise a single shaft (e.g.,102aand103aare integral portions of the same shaft), may be distinct from one another (e.g., shaft102aand shaft103bare separate individual shafts), or a combination thereof (e.g., shafts102aand103aare integral portions of the same shaft, shaft102bis a separate shaft from shaft103b). Each of the shafts described in connection withFIGS. 5A and 5Bmay be coupled to the corresponding planet gear such that the shaft rotates freely around said shaft's axis of rotation independent of the rotation of the planet gear (around the planet gear's axis of rotation), independent of the rotation of the carrier, or a combination thereof.

Referring toFIG. 5C, an orthogonal side view of a linkage110of speed control assembly170in accordance with an embodiment of the disclosure is shown. Linkage110generally comprises intermediate shafts111a,111b, and111c. Shaft111acouples planet gear112ato planet gear113a, shaft111bcouples planet gear112bto planet gear113b, and shaft111ccouples planet gear112cto planet gear113c. Intermediate shafts111a,111b, and111care affixed to planet gears112aand113a, planet gears112band113b, and planet gears112cand113c, respectively, such that the planetary rotations of intermediate shafts111a,111b, and111care in unison with planet gears112a,113a,112b,113b,112c,113caffixed thereto.

Referring again to the linkages shown inFIGS. 5A and 5B, one or both of the sun gears30,40,130,140may optionally be coupled to the nearest carrier21,22,101via an additional shaft, thereby providing additional mechanical support to regions of speed control assemblies150and160that are subject to the most intense of the internal stresses and strains during operation. Each optional shaft may rotate around the shaft's axis of rotation independent of the rotation of the sun gear, the carrier, or a combination thereof. Similarly, the sun gears230,240ofFIG. 5Cmay optionally be linked with a shaft to improve mechanical support.

It should be noted that the linkages shown inFIGS. 5A, 5B, and 5Care a few exemplary embodiments of linkages suitable for use in various speed control assemblies of the disclosure and are not intended to constitute an exhaustive list. For example, linkages suitable for use with mesh-type epicyclic or planetary gear subassemblies, step-type epicyclic or planetary gear subassemblies, multi-stage epicyclic or planetary gear subassemblies, or any combination thereof, also fall within the scope of the disclosure.

Referring now toFIGS. 6A, 6B, and 6C, oblique side views show the mechanical relationships between the components of the speed control assembly1, the first epicyclic or planetary gear subassembly14, and the second epicyclic or planetary gear subassembly24, respectively. The mechanical relationships shown inFIGS. 6A-6Cillustrate an exemplary embodiment wherein the input drive shaft12, the first epicyclic or planetary gear subassembly14, the second epicyclic or planetary gear subassembly24, and the linkage20may be configured such that a rotational speed of the rotatable gear adjusts a drive speed ratio ωo:ωi. Input drive shaft12may be integrally or mechanically coupled to sun gear30such that the rotation of input drive shaft12drives the rotation of sun gear30. As shown inFIGS. 3B, 6A, and 6Bsun gear30may engage each of planet gears32a,32b,32cby interlocking splines33of sun gear30distributed along an outer circumferential surface36of sun gear30with splines37a,37b, and37cdistributed respectively along outer circumferential surfaces38a,38b, and38cof planet gears32a,32b,32c. As shown inFIGS. 3C, 6A, and 6C, rotatable ring gear34may engage planet gears32a,32b,32cby interlocking inner splines29of the rotatable ring gear34, which are distributed along an inner circumferential surface35of the rotatable ring gear34with splines37a,37b, and37cof planet gears32a,32b,32c. The rotation speed adjustment device50may engage rotatable ring gear34by interlocking splines51of the rotation speed adjustment device50with outer splines31distributed along an outer circumferential surface39of the rotatable ring gear34. Similar to the first epicyclic or planetary gear subassembly14, the fixed ring gear44, planet gears42a,42b,42c, and sun gear40of the second epicyclic or planetary gear subassembly24are engaged via interlocking splines47a,47b,47c,43,45and output drive shaft18is integrally or mechanically coupled to sun gear40. The first and second carriers21and22may be coupled to the planet gears32a,32b,32c,42a,42b,42cof the first and second epicyclic or planetary gear subassemblies14,24as previously described herein. Intermediate shaft23may be fixedly coupled to the carriers21,22at opposite ends of intermediate shaft23, and may be integrally or mechanically joined to said carriers21,22such that the carriers21,22and the intermediate shaft23rotate at the same rotational speed.

The rotation speed adjustment device may comprise any means suitable for adjusting a rotatable speed of the rotatable gear. The rotation speed adjustment device50may be any device suitable for increasing a rotational speed of a rotatable gear, decreasing a rotational speed of a rotatable gear, stopping rotation of a rotatable gear, or any combination thereof. The rotation speed adjustment device may comprise a brake, a motor, any plurality thereof, or any combination thereof. Brakes suitable for the rotation speed adjustment device include but are not limited to a hydraulic brake, a hydraulic pump, an electric brake, a mechanical brake, an electromagnetic brake, any plurality thereof, or any combination thereof. Motors suitable for the rotation speed adjustment device include but are not limited to a hydraulic motor, an electric motor, a combustion engine, any plurality thereof, or any combination thereof, and specifically include otherwise existing motors within the airframe or on the vehicle.

The rotation speed adjustment device may be coupled to the rotatable gear, and may be configured to adjust the rotational speed ωrgof the rotatable gear coupled thereto. The rotation speed adjustment device may function as a brake, a drive motor, or a combination thereof in relation to the rotatable gear. In various embodiments of the first gear subassembly, the rotation speed adjustment device may drive axial counter-rotation of the rotatable gear relative to axial rotation of the sun gear, to the axial rotation of the rotatable gear in the same direction as the axial rotation of the sun gear, or, at different times, a combination thereof. In an embodiment the rotation speed adjustment device comprises a counter-rotation device coupled to a rotatable ring gear of an epicyclic or planetary gear subassembly and configured to adjust a speed of counter-rotation of the rotatable ring gear relative to a sun gear of the epicyclic or planetary gear subassembly. The rotation speed adjustment device may engage the rotatable gear by interlocking splines distributed around an outer circumferential surface of the rotation speed adjustment device with splines distributed around an outer circumferential surface of the rotatable ring gear.

In some embodiments, the rotatable gear may be a gear other than a ring gear. For example, the rotatable gear may be a planet gear or a sun gear. In an embodiment, the rotatable gear comprises a sun gear. Referring toFIG. 7, an orthogonal side view of a speed control assembly1200comprising a rotatable sun gear1230in accordance with an embodiment of the disclosure is shown. Speed control assembly1200comprises an input drive shaft1210coupled to one or more planet gears1250of a first epicyclic or planetary gear subassembly1410, an output drive shaft1220coupled to one or more planet gears1260of a second epicyclic or planetary gear subassembly1420, and a linkage1290coupling a ring gear1310of the first epicyclic or planetary subassembly1410to a ring gear1320of the second epicyclic or planetary gear subassembly1420. Carrier1270of the first epicyclic or planetary gear subassembly1410may be coupled to the input drive shaft1210and supports each of the one or more planet gears1250, allowing coordinated planetary rotational movement of each of the one or more planet gears1250. Each of the planet gears1250are coupled to and mechanically engaged with a rotatable sun gear1230of the first epicyclic or planetary gear subassembly1410and ring gear1310. Rotatable sun gear1230may be coupled to and mechanically engaged with rotation speed adjustment device1300. Rotation speed adjustment device1300comprises a drive motor1330which drives a gear1340. Gear1340may be coupled to and mechanically engaged with rotatable sun gear1230.

Carrier1280of the second epicyclic or planetary gear subassembly1420may be coupled to the output drive shaft1220and supports each of the one or more planet gears1260, allowing coordinated planetary rotational movement of each of the one or more planet gears1260. Each of planet gears1260are coupled to and mechanically engaged with a fixed sun gear1240of the second epicyclic or planetary gear subassembly1420and ring gear1320. Ring gears1310and1320are coupled together via linkage1290, but are otherwise free to rotate.

Still referring toFIG. 7, rotation of the input drive shaft1210may be facilitated by bearings1400a,1400b,1380a,1380b. Rotation of the output drive shaft1220may be facilitated by bearings1380a,1380b,1380c,1380d. Rotation of the sun gear1230may be facilitated by bearings1370a,1370b,1370c,1370b,1400a,1400b. The input drive shaft1210may be coupled to one or more of the planet gears1250such that rotation of the input drive shaft1210may drive planetary rotation of the one or more planet gears1250in the same direction as the input drive shaft1210. The output drive shaft1220may be coupled to one or more of the planet gears1260such that planetary rotation of the one or more planet gears1260drives rotation of the output drive shaft in the same rotational direction as the planetary rotations of the one or more planet gears1260. Rotation speed adjustment device1300may be used to adjust the drive speed ratio ωo:ωiof speed control assembly1200by controlling the rotational speed of rotatable sun gear1230. For example, rotation speed adjustment device1300may be used to counter-rotate sun gear1230such that output drive shaft1220rotates at a rotational speed less than the rotational speed of input drive shaft1210(e.g., ωo:ωidecreases). Planetary rotation of the one or more planet gears1250in the same rotational direction as input drive shaft1210may be offset by the counter-rotation of the rotatable sun gear1230as the one or more planet gears1250are couple to and mechanically engaged with both the input drive shaft1210and the rotatable sun gear1230at the same time.

In various embodiments, motor1330and gear1340may be replaced with a brake that is coupled to ring gear1310or any gear of the second epicyclic or planetary gear subassembly1420. In such cases, when the input shaft is spinning and the brake is applied, the sun gear1230will spin freely.

The speed control assembly in accordance with various embodiments of the disclosure may be used to rotate any rotating part of any mechanical device. In various embodiments, a speed control assembly in accordance with an embodiment of the disclosure drives rotation of a thrust-providing mechanical device. The output drive shaft may rotate a rotor, a propeller, an impeller, a screw (e.g., the screw of a screw-propelled vehicle), any plurality thereof, or any combination thereof. In an embodiment, a speed control assembly of the disclosure drives rotation of a tail rotor of a helicopter. The speed control assembly may couple the helicopter's engine to the tail rotor within a fuselage of a helicopter. In an embodiment, the helicopter engine may be coupled to the input drive shaft of the speed control assembly and the output drive shaft of the speed control assembly may be coupled to the tail rotor of the helicopter. In another embodiment, the speed control assembly of the disclosure drives rotation of a submersible propeller.

Referring now toFIGS. 8A, 8B, and 8C, oblique side views of a speed control assembly710illustrate a method of controlling an auxiliary rotor in accordance with an embodiment of the disclosure. The method of controlling the speed of an auxiliary rotor771may generally comprise rotating an input drive shaft702driven by an output shaft700of an engine or motor of a primary rotor and coupled to an epicyclic or planetary gear sub-assembly714comprising a rotatable ring gear734. For example, an input drive shaft702rotates at a rotational speed ωi. Input shaft702may be coupled to sun gear730such that input drive shaft702and sun gear730rotate in unison at rotational speed ωi. A method of controlling the speed of an auxiliary rotor also comprises driving an output drive shaft coupled to the auxiliary rotor by rotating the input shaft. From the arrows, it may be seen that clockwise rotation of input shaft702drives a clockwise rotation of sun gear730, which in turn drives counterclockwise axial rotation of planet gears732a,732b,732c, and the axial rotations of planet gears732a,732b,732cdrive a clockwise planetary rotation of planet gears732a,732b,732caround sun gear730. Clockwise planetary rotation of planet gears732a,732b,732cin turn drive the clockwise planetary rotation of shafts761a,761b,761c. The clockwise planetary rotations of761a,761b,761c, each of which are coupled to planet gears732a,732b,732c, respectively, at one end and to carrier721at the other, drive clockwise rotation of carrier721, shaft723, and carrier722. Carrier721, shaft723, and carrier722may be integrally formed such that carrier721, shaft723, and carrier722rotate in unison at rotational speed ω1. The clockwise rotation of carrier722drives the planetary rotation of shafts772a,772b,772cand planet gears742a,742b,742cby way of a configuration similar to that shared between carrier721, shafts761a,761b,761c, and planet gears732a,732b,732c. The clockwise rotation of carrier722also drives the counterclockwise axial rotation of planet gears742a,742b,742c. Because gear ring744is fixed in place, 100% of the planetary and axial rotations of planet gears742a,742b,742cdrive the clockwise rotation of sun gear740and output drive shaft718, which may be coupled to sun gear740such that sun gear740and output drive shaft718rotate in unison at rotational speed ωo. Thus,FIGS. 8A-8Cillustrate an embodiment of the disclosure whereby rotation of an input drive shaft drives an output drive shaft coupled to an auxiliary rotor.

Still referring toFIGS. 8A-8C, the method of controlling the speed of an auxiliary rotor may also comprise adjusting a drive speed ratio ωo:ωi, by controlling a rotational speed of the rotational ring gear734. In an embodiment, the rotatable ring gear734rotates axially opposite to the axial rotation of the input drive shaft. This counter-rotation of rotatable ring gear734drives axial and planetary rotation of planet gears732a,732b,732cin a rotational direction opposite to the axial rotation of input drive shaft702, thus reducing the net planetary and axial rotational speeds of planet gears732a,732b,732c. The decrease in the planetary rotational speed of planet gears732a,732b,732ccarries through to output drive shaft718by way of the mechanical relationships of the components of the speed control assembly therebetween, resulting in a reduced drive speed ratio ωo:ωi. Thus,FIGS. 8A-8Cillustrates an embodiment of the disclosure wherein the drive speed ratio ωo:ωi, is adjusted by controlling the rotational speed of a rotatable gear.

Still referring toFIGS. 8A-8C, in various embodiments the rotatable gear734may be prevented from rotating, or even reversed. As a result, the rotational speed ωoof output drive shaft718is not altered by counter-rotation of rotatable gear734. In an embodiment, the gear ratios of the first and second epicyclic or planetary subassembly gears are selected so as to provide a ωo:ωiratio of 1:1 when the rotatable ring gear is held stationary. The rotatable ring gear may be held stationary by a rotation speed adjustment device such as a brake or a drive motor delivering a tangential counterforce sufficient to suppress counter-rotation of the rotatable ring gear734.

In some embodiments, the method of controlling the speed of an auxiliary rotor771allows for the free rotation of the rotatable gear without any interference from the rotation speed adjustment device750. Counter-rotation of the rotatable ring gear734relative to the rotation of the input drive shaft702may be induced by axial rotation of input drive shaft702itself. While not wishing to be limited by theory, it is believed that angular momentum from the rotation of input drive shaft702is conveyed to rotatable ring gear734through the chain of mechanically interlinked components connecting the rotatable ring gear734to input drive shaft702, inducing counter-rotation of rotatable ring gear734. This operating state (e.g., free counter-rotation of rotatable ring gear734driven by the rotation of input drive shaft702) may be advantageous in that additional energy is not required to operate a rotation speed adjustment device in order to reduce the rotational speed of the output drive shaft718, an auxiliary rotor771coupled to the output drive shaft718, or a combination thereof.

In an embodiment, the rotatable ring gear734may counter-rotate relative to a rotation of the input drive shaft702at a speed sufficient to stop rotation of the output drive shaft718. While not wishing to be bound by theory, it is believed that the contribution to the speed of planetary rotation of planet gears732a,732b,732cattributable to axial rotation of the input drive shaft702is equal in magnitude and opposite in sign to the contribution to the speed of planetary rotation of planet gears732a,732b,732cattributable to the counter-rotation of rotatable ring gear734. In an embodiment, the rotation speed adjustment device increases the rate of counter-rotation of the rotatable ring gear734beyond the rotational speed achieved by the rotatable ring gear734in a freely spinning state. Increasing the rate of counter-rotation beyond the rotational speed of the rotatable ring in a freely spinning state may compensate for frictional inefficiencies, other mechanical inefficiencies of the speed control assembly710, and the angular momentum of the input drive shaft702lost to downstream components of the speed control assembly710.

In some embodiments, the rotating of the rotatable ring gear734is controlled using a brake, a motor, a pump, or a combination thereof. In some embodiments, the method of controlling the speed of an auxiliary rotor comprises rotating the auxiliary rotor coupled to the output drive shaft at a speed different than the speed of a primary rotor coupled to the input drive shaft. The difference in speed may be the result of the gear ratios chosen for the individual gear assemblies, the result of counter-rotation of the rotatable ring gear, the result of adjustment of the rotational speed of the rotational ring gear via a rotation speed adjustment device, or any combination thereof.

Various methods of controlling the speed of an auxiliary rotor embodied herein may be utilized to control the tail rotor of a helicopter. In an embodiment, the method of controlling the speed of an auxiliary rotor is utilized to control the noise generated by the helicopter tail rotor by adjusting the drive speed ratio ωo:ωi, of the input and output drive shafts. The drive speed ratio ωo:ωimay be adjusted by adjusting the speed of the rotatable gear (ωrg) relative to the speed of the input drive shaft (ωi). In some embodiments, the method of controlling the speed of an auxiliary rotor is utilized such that the rotational speed of the tail rotor of a helicopter may be controlled independent of a primary rotor of the helicopter. The counter-rotation of the rotatable ring gear, which may be assisted by a rotation speed adjustment device, allows the rotational speed of the auxiliary rotor to be adjusted without changing the rotational speed of the primary rotor. Methods of controlling the speed of an auxiliary rotor in accordance with various embodiments of the disclosure may be used to maintain a rotational speed of a helicopter while a rotational speed of a primary rotor of the helicopter varies.

FIG. 9illustrates an exemplary embodiment of a method of adjusting noise of a helicopter tail rotor according to an embodiment of the disclosure. For simplicity, the equations ofFIG. 9assume (1) use of a speed control assembly similar in design to the speed control assembly1ofFIG. 2; and (2) that all mechanically engaged gears of the speed control assembly share a 1:1 gear ratio. From blocks804,816it may be seen that the tail rotor rotates faster than and in the same direction as the input shaft of the speed control assembly when ωrg>0. From blocks806,818it may be seen that the tail rotor rotates in the same direction and at the same speed as the input shaft of the speed control assembly when ωrg=0. From blocks808,820it may be seen that the tail rotor rotates in the same direction but slower than the input shaft of the speed control assembly when −ωi<ωrg<0. From blocks810,822it may be seen that the tail rotor stops when ωrg=−ωi. From blocks812,824it may be seen that the tail rotor rotates opposite to but slower than the input shaft of the speed control assembly when −2ωi<ωrg<0. From blocks814,826it may be seen that the tail rotor rotates opposite to and faster than the input shaft of the speed control assembly when −ωrg<−2ωi<0. FromFIG. 9, it may be seen speed control assemblies according to various embodiments of the disclosure may facilitate broad control over the speed of a helicopter tail rotor independent of the velocity of an input drive shaft. However, the mathematical relationships shown inFIG. 9are provided for the purposes of illustration only, and it should be understood that the relationships illustrated in blocks804,806,808,810,812,814and also the functionality illustrated in blocks816,818,820,822,824,826may vary as a function of the control scheme for and the design of the speed control assembly.

In various embodiments, the method of controlling the speed of an auxiliary rotor may further comprise adjusting the noise generated by a tail rotor of a helicopter coupled to the output drive shaft. By increasing a counter-rotation of a rotational gear of a speed control assembly in accordance with an embodiment of the disclosure a speed of a helicopter tail rotor coupled to an output drive shaft may be reduced, thus lowering the noise generated by the helicopter tail rotor. When the speed of a main rotor of a helicopter is increased, the input drive shaft to the speed control assembly also increases. To counter-act the increase in noise that would otherwise occur from a faster-rotating helicopter tail rotor, the counter-rotation of the rotatable ring of the speed control assembly may be increased to prevent all or some of the increase in the speed of the tail rotor, thus preventing all or some of the additional noise that would have otherwise been generated by the tail rotor. In other embodiments where the auxiliary rotor comprises the tail rotor of a helicopter, a method of controlling the speed of an auxiliary rotor may be used to adjust the noise generated by the tail rotor over a change in altitude by adjusting the drive speed ratio ωo:ωi. Although not wishing to be bound by theory, it is believed that the noise generated by a helicopter tail rotor varies as a function of tail rotor speed, of the thickness of the air at different altitudes, and by the distance between the helicopter tail rotor and a listener.

The flow diagrams ofFIGS. 10A-10Cillustrate a method of adjusting noise of a helicopter tail rotor in accordance with an embodiment of the disclosure. For simplicity, the rotational velocity of the input drive shaft is assumed constant between adjacent blocks except where otherwise indicated by one of the blocks. The upward pointing arrows shown in brackets indicate that the variable directly above has increased as a result of the action indicated in the preceding block. The downward pointing arrows shown in brackets indicate that the variable directly above has decrease as a result of the action indicated in the preceding block. Blocks918,920,902,904,934,936illustrate that, given a constant tail rotor speed, a decrease in altitude increases and an increase in altitude decreases the noise generated by a helicopter tail rotor. Blocks906,908,910,922,924,926,938,940,942illustrate that increasing the counter-rotational velocity of the rotatable gear ωrgreduces the tail rotor noise by reducing the velocity of the output drive shaft. Blocks918,902,904,906,908,910illustrate that increased rotor noise associated with a decrease in altitude can be at least partially offset by increasing the counter-rotational velocity of the rotatable gear ωrg. Blocks912,914,916,928,930,932,944,946,948illustrate that decreasing the counter-rotational velocity of the rotatable gear ωrgincreases the tail rotor noise by reducing the velocity of the output drive shaft. Blocks918,934,936,944,946,948illustrate that decreased noise associated with an increase in altitude may be at least partially offset by decreasing the counter-rotational velocity of the rotatable gear ωrg, which may be advantageous in instances where the higher speeds of the tail rotor are needed to provide greater maneuverability of and control over the helicopter. Thus, various embodiments of the speed control assembly and methods of controlling an auxiliary rotor described herein may advantageously provide improved control over tail rotor noise and helicopter maneuverability over a greater range of operational conditions.

Various embodiments of the speed control assemblies and methods of controlling the speed of an auxiliary rotor disclosed herein may advantageously allow the tail rotor of a helicopter to be held at rest while a primary rotor of the helicopter continues to operate at operational or standby speeds to rotate at substantially reduced speeds in comparison to the speed of the tail rotor in the absence of counter-rotation of a rotation velocity adjustment device; or a combination thereof. Various embodiments of the speed control assemblies and methods of controlling the speed of an auxiliary rotor disclosed herein may also advantageously allow a pilot, computer, or a combination thereof to select tail rotor speeds independent of the main rotor of the helicopter (e.g., the speed of the tail rotor may be adjusted without requiring further adjustment to the speed of the primary rotor. By providing a means for independently controlling the speed of a helicopter tail rotor, the safety of operating a helicopter may advantageously be improved, especially in those situations where bystanders, passengers, crew, or any combination thereof are exposed to the tail rotor, such as during standby, loading, boarding, disembarking, landing, and takeoff. In addition, the speed control is accomplished while maintaining a positive mechanical linkage between the engine and the tail rotor.

In various embodiments, speed control assemblies and methods of controlling an auxiliary rotor of the disclosure may be utilized to maneuver rotor-propelled vehicles. For example, by coupling a speed control assembly in accordance with an embodiment of the disclosure to a tail rotor of a helicopter, the independent control of the tail rotor speed may facilitate maneuvering of the helicopter by providing the helicopter pilot with an additional degree of freedom (e.g., independent rotation of the tail rotor) with which to control the direction and movement of the helicopter. Rotation of the primary rotor may be adjusted by a pilot to achieve one navigational objective (e.g., a change in altitude), while the drive speed ratio ωo:ωimay be adjusted to achieve a second navigational objective (e.g., orientation of the helicopter).

In some embodiments, a speed control assembly of the disclosure, a method of controlling the an auxiliary rotor, or a combination thereof may be utilized to manage the noise generated by a tail rotor of a rotorcraft over a range of altitudes without sacrificing maneuverability of the rotorcraft.