Drive system utilizing a differential for phase optimized contra-rotating coaxial rotors and methods thereof

Abstract

Systems and methods for a drive system are disclosed. The drive system includes: a motor (120) operably coupled to an input shaft (115) at a first end, wherein the motor is configured to cause the input shaft to rotate in a first direction at a first angular velocity; a first output shaft (105) configured to rotate in the first direction at the first angular velocity; a second output shaft (110) configured to rotate in a second direction, opposite the first direction, at the first angular velocity; a cage component (150) housing the gear assembly, wherein rotation of the cage component is configured to cause the second output shaft to rotate at a second angular velocity, rotation of the second output shaft at the second angular velocity causing an adjustment in a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades.

Description

DRIVE SYSTEM UTILIZING A DIFFERENTIAL FOR PHASE OPTIMIZED CONTRA-ROTATING COAXIAL ROTORS AND METHODS THEREOFCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 617,252, filed January 3, 2024, which is incorporated by reference herein in its entirety.FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to embodiments of a drive system that utilize a differential gear set for splitting power into two contra-rotating outputs, and, more specifically, to a drive system that enables the control and optimization of the blade crossing azimuth in contra rotating propellers by adjusting characteristics of the differential gear set.BACKGROUND

[0003] Differential gear sets have been extensively utilized in the aircraft and marine industries in contra-rotating propeller systems. These gear sets enable the conversion of a single power input shaft into two concentric outputs with opposite rotation. Conventionally, differential gear sets have been employed in static configurations, whereby the cage portion of the differential is rigidly fixed to a structure of the propeller assembly. In this configuration, the azimuth of the contra rotating propellers is typically fixed at a predetermined location. Adjusting theazimuth typically requires disassembly and repositioning of various shafts and gears in the drive system, which may be time-consuming and burdensome.

[0004] The present disclosure is accordingly directed to an improved vehicle drive system that employs a rotating cage portion that houses the differential gear set. Rotation of the cage portion enables adjustment and optimization of the bladecrossing azimuth between a set of contra-rotating propellers without requiring manual user intervention. The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art, or suggestions of the prior art, by inclusion in this section.SUMMARY OF THE DISCLOSURE

[0005] According to certain aspects of the disclosure, systems and methods are disclosed for an adjustable differential gear set of a vehicle drive system.

[0006] In one aspect, a drive system is provided. The drive system may include a motor operably coupled to an input shaft at a first end, wherein operation of the motor is configured to cause the input shaft to rotate in a first direction at a first angular velocity. The drive system may further include a first output shaft coupled to the input shaft at a second end of the input shaft, wherein the first output shaft is configured to rotate in the first direction at the first angular velocity. The drive system may further include a second output shaft operatively coupled to the input shaft via a gear assembly including a plurality of gears, wherein the second output shaft is configured to rotate in a second direction, opposite the first direction, at the first angular velocity. The drive system may further include a cage component housingthe gear assembly, wherein the cage component is configured to be rotatable about a central rotor axis and wherein rotation of the cage com ponent is configured to cause the second output shaft to rotate at a second angular velocity and wherein rotation of the second output shaft at the second angular velocity causes an adjustment in a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades.

[0007] In another aspect, an aircraft is provided. The aircraft may include a first set of propeller blades. The aircraft may further include a second set of propeller blades. The aircraft may further include a drive system that includes: a motor operably coupled to an input shaft; a first output shaft connected to the input shaft and to the first set of propeller blades; a second output shaft operatively coupled to the input shaft via a plurality of gears and to the second set of propeller blades; and a cage component that houses the plurality of gears. The cage component of the drive system may be configured to rotate about a central rotor axis and wherein rotation of the cage component causes an adjustment to an angular velocity at which the second set of propeller blades spin, wherein the adjustment to the angular velocity adjusts a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades from a first position to a second position.

[0008] In yet another aspect, a method of adjusting a position of a bladecrossing azimuth at which a first set of propellers of an aircraft crosses a second set of propellers is disclosed. The method includes: receiving, at a differential drive system of the aircraft, an input to adjust an angular velocity at which the second set of propellers spin. The method further includes controlling, using an actuator device, a cage component connected to the differential drive system to rotate by a predetermined amount based on the input. The method further includes adjusting,upon rotation of the cage component, the angular velocity of an output shaft connected to the second set of propellers.

[0009] Additional objects and advantages of the disclosed embodiments will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the disclosed embodiments. The objects and advantages of the disclosed embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments, as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the disclosed embodiments, and together with the description, serve to explain the principles of the disclosed embodiments. There are many aspects and embodiments described herein. Those of ordinary skill in the art will readily recognize that the features of a particular aspect or embodiment may be used in conjunction with the features of any or all of the other aspects or embodiments described in this disclosure. In the drawings:

[0012] FIG. 1A depicts a geared differential drive system in a fixed cage position, according to various aspects of the present disclosure.

[0013] FIG. 1 B depicts the geared differential drive system in a rotated cage position, according to various aspects of the present disclosure.

[0014] FIG. 2A depicts an overhead view of a set of contra-rotating propeller blades with an indication of a first blade-crossing azimuth position, according to various aspects of the present disclosure.

[0015] FIG. 2B depicts the set of contra-rotating propeller blades in FIG. 2A in a crossed state at the first blade-crossing azimuth position, according to various aspects of the present disclosure.

[0016] FIGS. 3A depicts an overhead view of the set of contra-rotating propeller blades in FIG. 2A with an indication of a second blade-crossing azimuth position, according to various aspects of the present disclosure.

[0017] FIG. 3B depicts the set of contra-rotating propeller blades in FIG. 3A in a crossed state at the second blade-crossing azimuth position, according to various aspects of the present disclosure.

[0018] FIG. 4A depicts a friction-based differential drive system in a first configuration, according to various aspects of the present disclosure.

[0019] FIG. 4B depicts the friction-based differential drive system in a second configuration, according to various aspects of the present disclosure.DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0020] The terminology used below may be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the present disclosure. Indeed, certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section. Both the foregoing general description and thefollowing detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed.

[0021] In this disclosure, the term “based on” means “based at least in part on.” The singular forms “a,” “an,” and “the” include plural referents unless the context dictates otherwise. The term “exemplary” is used in the sense of “example” rather than “ideal.” The terms “comprises,” “comprising,” “includes,” “including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, or product that comprises a list of elements does not necessarily include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. Relative terms, such as, “substantially” and “generally,” are used to indicate a possible variation of ±10% of a stated or understood value.

[0022] Embodiments of the present disclosure may be incorporated into an aircraft. As used herein, “aircraft” may refer to an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, vessel, or virtually any other vehicle moving, or capable of moving, through air. Some non-limiting examples may include a helicopter, an airship, a hot air balloon, a vertical take-off craft (e.g., an electric vertical take-off and landing (eVTOL)), an unmanned aerial vehicle, or a drone.

[0023] Vehicles employing propeller systems are commonly used to transport people and / or objects from one location to another. Some propeller systems utilize two coaxial rotors in which one rotor is mounted above the other and each rotor is coupled to a set of propeller blades. The two rotors may be configured to contrarotate (i.e. , rotate in opposite directions around the same axis). The presence and utilization of the two coaxial rotors negates the need for a tail rotor and providessymmetry of forces around the central axis during vehicle liftoff and during lateral movement in flight. Vehicles outfit with coaxial rotors also tend to be able to handle an increased payload, produce less noise, and may be designed to be more compact than single rotor vehicles in order to operate in areas where space is at a premium (e.g., the decks of ships, etc.).

[0024] When properly aligned with the inflowing airstream, the contra-rotation of the propellers produces equal and opposite hub moments that cancel out, which correspondingly prevents potentially harmful vibratory loads from being passed onto the vehicle airframe. Larger vibrations, however, may be created and passed to the airframe when unequal and non-opposite hub moments are created (e.g., when the inflowing air is no longer in proper alignment with the azimuth location of the propeller blades). In order to handle these larger vibrations, the weight of the propeller system and / or the vehicle airframe needs to be increased, which may correspondingly increase the rate of fuel consumption and generate higher operating costs.

[0025] Conventionally, differential gear sets have been utilized to transmit power from an engine to the coaxial rotor pair. A cage portion of the differential gear set is typically rigidly fixed, thereby locking the blade crossing azimuth of the propellers at a specific location. In these conventional configurations, adjustment of the azimuth location could only be achieved by disassembling and repositioning components (e.g., gears, shafts, etc.) of the differential gear set, which may be timeconsuming and burdensome. Additionally, these conventional restrictions prevent substantially real-time adjustment and optimization of the azimuth location to adapt to varying flight conditions. More particularly, because the inflow angle of an airstream with respect to the propellers varies with the direction of flight and / or theprevailing winds, it is necessary for the aircraft to actively manage the azimuth location during certain portions of flight (e.g., during lift rotor operation). A need therefore exists for a simple, mechanical mechanism that is capable of substantially real-time azimuth control between the contra-rotating propellers.

[0026] Accordingly, the present disclosure provides a novel drive assembly that is capable of real-time azimuth control and optimization within contra-rotating propeller systems. More particularly, the novel assembly may be leveraged to produce variations in the revolutions per minute (RPM) between the coaxial rotors to change the azimuth location of the blade passage to align with the inflow of the airstream. By enabling precise azimuth adjustments without the need for gear set disassembly or repositioning, the novel assembly empowers users and / or aircraft systems to control the azimuth location in substantially real-time. This level of control may enable adjustments to be made to the propeller system to account for the vibratory forces that may be incurred during a variety of different operating conditions. Furthermore, the presence of real-time azimuth control may also enable lighter vehicle designs to be employed, which may be more operationally efficient.

[0027] The subject matter of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments. An embodiment or implementation described herein as “exemplary” is not to be construed as preferred or advantageous, for example, over other embodiments or implementations; rather, it is intended to reflect or indicate that the embodiment(s) is / are “example” embodiment(s). Subject matter may be embodied in a variety of different forms and, therefore, covered or claimed subject matter is intended to be construed as not being limited to any exemplary embodiments set forth herein;exemplary embodiments are provided merely to be illustrative. Likewise, a reasonably broad scope for claimed or covered subject matter is intended. Among other things, for example, subject matter may be embodied as methods, devices, components, or systems. The following detailed description is, therefore, not intended to be taken in a limiting sense.

[0028] Throughout the specification and claims, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, the phrase “in one embodiment” or “in some embodiments,” or “in one aspect” or “in some aspects” as used herein does not necessarily refer to the same embodiment or aspect, and the phrase “in another embodiment” or “in another aspect” as used herein does not necessarily refer to a different embodiment or aspect. It is intended, for example, that claimed subject matter include combinations of exemplary embodiments in whole or in part.

[0029] Referring to FIG. 1A, first differential drive system 100 is illustrated according to one or more aspects of the present disclosure. In an aspect, first differential drive system 100 may be configured to split power from an input source (e.g., an electric motor) into two co-axial, contra-rotating outputs of equal and opposite RPM, i.e. , first output shaft 105 (e.g., an “inner output shaft”) and second output shaft 110 (e.g., an “outer output shaft”). Input shaft 115 may be operatively coupled to the motor 120 at first end 125 that causes input shaft 115 to rotate in a first direction at angular velocity coi . Inner output shaft 105 may be integrally coupled to input shaft 115 at second end 130, opposite first end 125, and may therefore always also rotate in the first direction and at the same angular velocity coi as input shaft 115.

[0030] Outer output shaft 110 may be caused to rotate in a second direction, opposite the first direction, at angular velocity - coi , using power received from input shaft 115 through a particular differential gear path. More particularly, rotation of input shaft 115 may cause first gear 135 to rotate (rotation from right to left being shown in FIG. 1A). Second gears 140A, OB may be connected to first gear 135 and may be caused to rotate in opposite directions with respect to one another via rotation of first gear 135. In one aspect, second gears 140A, MOB may be planetary gears. The rotation of second gears 140A, MOB may cause third gear 145 to rotate, which may correspondingly facilitate the rotation of outer output shaft 110. In an aspect, first gear 135 may have an equivalent number of gear teeth as third gear 145.

[0031] First differential drive system 100 may further include differential cage 150 that is mounted around the gear path / assembly in a way that allows rotation of differential cage 150 about the central rotor axis. Gears 140A and MOB are attached to differential cage 150 via bearings. Differential cage 150 may be in mesh with fourth gear 160 (e.g., a worm gear) that, when fixed in place, fixes the blade-crossing azimuth (i.e. , the position at which a first set of propeller blades crosses a second set of propeller blades) of the two coaxial rotors in a set location. More particularly, because first gear 135 and third gear 145 each have equal tooth numbers, second gears 140A, MOB may act as idlers and enable inner output shaft 105 and outer output shaft 110 to rotate in opposite directions at equal RPM, thereby splitting the input power equally between the outputs (ignoring frictional losses). In this state, when the blade-crossing azimuth is properly aligned with the inflowing airstream, rotation of the first and second set of propeller blades associated with inner output shaft 105 and outer output shaft 110, respectively, create equal and opposite hubmoments that are resolved between output shaft bearings 155 and do not pass any vibratory loads into the airframe structure.

[0032] During flight, the vehicle may perform various maneuvers that cause the blade-crossing azimuth to no longer be in proper alignment with the inflow of air. In these situations, a user of the vehicle (e.g., a pilot) or an automated control system may provide inputs that cause differential drive system 100 to create a differential speed (e.g., as measured in revolutions per minute or “RPM’) between inner output shaft 105 and outer output shaft 110. This RPM differential may change the angular position of the blade crossing azimuth to a desired position, e.g., a position in which the azimuth is again in alignment with the inflowing airstream. To facilitate this change, in one aspect, an RPM input may be provided to differential cage 150 by actuating fourth gear 160. Actuation of fourth gear 160 may be facilitated by utilization of an actuation device, e.g., a solenoid, a cable system, etc. Actuated fourth gear 160 may cause differential cage 150 to rotate in the second direction (rotation from left to right being shown in FIB. 1 B) by a desired angular velocity C02, as shown in FIG. 1 B.

[0033] The cage rotation correspondingly creates a differential speed (e.g., RPM) between inner output shaft 105 and outer output shaft 110, as shown in FIG. 1 B. More particularly, although inner output shaft 105 maintains angular velocity coi , rotation of differential cage 150 in the second direction (i.e., in the same direction as outer output shaft 110) by angular velocity C02 causes outer output shaft 110 to rotate at an increased angular velocity of -wi + 2(co2). This change in angular velocity may enable a user to establish any desired azimuth position (e.g., based on operating and / or weather conditions). Once the azimuth is set at the desired position, differential cage 150 may be locked and the RPM input to fourth gear 160 may bereversed. More particularly, fourth gear 160 may be caused to drive backward, thereby returning inner output shaft 105 and outer output shaft 110 to their initial operating state of equal and opposite RPMs.

[0034] In an aspect, vehicle control system 170 may receive input 165 from one or more sources. For instance, in one aspect, the pilot of the vehicle may manually control when an RPM input is provided to differential cage 150 and may also designate the exact value of the input (e.g., via interaction with various control components such as buttons, switches, handles, digital inputs, etc.). In another aspect, input 165 may be dynamically provided to control system 170. For instance, data may be captured by one or more vehicle sensors (e.g., wind speed, wind direction, propeller alignment with respect to wind direction, etc.) and may be transmitted to control system 170, e.g., in substantially real time. Control system 170 may process the received data and dynamically determine whether an adjustment should be made to the blade-crossing azimuth position and the degree to which the adjustment should be implemented. Additionally or alternatively, the control system 170 may be configured to implement azimuth adjustments in response to predetermined events and / or at predetermined points during flight (e.g., during liftoff, during flight direction change, etc.). In an aspect, control system 170 may transmit instructions to actuator 175, which may subsequently control rotation of fourth gear 160 based on an input designation. In an aspect, only minor RPM inputs need to be applied to differential cage 150 to facilitate meaningful azimuth adjustments. For instance, a baseline RPM of output shafts 105, 110 may be approximately 1000RPMs. To institute a 45 degree azimuth adjustment, only a 10 - 15 RPM input needs to be applied to differential cage 150.

[0035] Although illustrated in FIGS. 1A and 1 B as being driven by a worm gear (i.e., fourth gear 160), such a designation is not limiting and differential cage150 may be actuated by another component. More particularly, fourth gear 160 may be replaced with any other mechanism to rotate differential cage 150, such as a spur, bevel, or face gear drive, cables, rotary actuators, etc. Additionally, the types of gears utilized in the gear assembly may also vary based upon a desired design configuration.

[0036] Other forms of differential gear systems may be utilized to achieve the same outcome as accomplished by first differential drive system 100. For instance, spur, face gear, or epicyclic differentials may be utilized in place of the bevel differential. Spur and face gear differentials may function the same as the bevel configuration when rotating the differential cage. Additional gearing stages may also be integrated into the differential assembly to provide an RPM reduction from the input to both outputs, thereby allowing for a smaller and more compact primary driver. It is important to emphasize, however, that although characteristics between the possible gearing systems may vary, each viable gearing system may contain a capability to implement a differential to at least one set of propeller blades to facilitate a blade-crossing azimuth adjustment.

[0037] Referring collectively to FIGS. 2A and 2B and FIGS. 3A and 3B, a nonlimiting example illustration of the adjustment of the blade-crossing azimuth position between a first and second set of propeller blades is provided. In FIG. 2A, first set of propeller blades 205 and second set of propeller blades 210 are shown to be contrarotating, e.g., rotating in opposite directions on a single axis as indicated by the directional arrows. At an original position, the blade-crossing azimuth may occur at position P1. More particularly, the blades of first set of propeller blades 205 andsecond set of propeller blades 210 cross at position P1 , as depicted in FIG. 2B.When the blade-crossing azimuth position of first and second set of propeller blades205, 210 is aligned with incoming wind flow 215 (e.g., the crossed position of propeller blades is oriented perpendicular to incoming wind flow 215), the vibratory loads experienced by the aircraft are reduced.

[0038] Referring now to FIGS. 3A and 3B, in situations where the direction of incoming wind flow 215 changes (e.g., as a result of changing weather conditions, aircraft maneuvers, etc.), the blade-crossing azimuth position of first and second set of propeller blades 205, 210 may be adjusted in-flight to account for this change. For instance, FIGS. 3A and 3B illustrate that incoming wind flow 215 has changed direction relative to the direction depicted in FIGS. 2A and 2B. Inputs may be provided to a differential drive system to adjust the rotational speed of at least one of first or second set of propeller blades 205, 210 so that the blade-crossing azimuth position changes, e.g., to position P2, to align with the new incoming wind direction.

[0039] Referring collectively to FIG. 4A and 4B, a non-limiting example of a continuously variable transmission (CVT) traction drive system 400 is illustrated according to one or more aspects of the present disclosure. CVT traction drive system 400 is another potential system that may be leveraged to facilitate adjustments to a blade-crossing azimuth between aircraft propellers during flight. Unlike first differential drive system 100, CVT traction drive system 400 may facilitate azimuth adjustments without the utilization of a gear assembly. More particularly, CVT drive system 400 may be a “friction drive” system 400 with no gear teeth or mechanical locking mechanisms, as further described herein.

[0040] In an aspect, input shaft 405 may be operatively connected to a motor 402 at a first end of input shaft 405 that causes input shaft 405 to rotate in a firstdirection at a first angular velocity coi . First disc 410 (e.g., a “primary” or “input disc”) may be integrally coupled to input shaft 405 and may correspondingly be caused to rotate in the first direction at the first angular velocity coi when first input shaft 405 is caused to rotate. First output shaft 415 (which may be connected to a first set of propeller blades (not illustrated)) may be integrally coupled to input shaft 405 at a second end of input shaft 405, opposite the first end of shaft 405, and may therefore always also rotate in the first direction at the first angular velocity coi .

[0041] One or more trunnions 420 may be positioned between first disc 410 and second disc 425 (e.g., a “secondary” or “output disc”) and second disc 425 may itself be connected to and facilitate the rotation of second output shaft 430 (which may be connected to a second set of propeller blades (not illustrated)). In an aspect, torque may be transferred from first disc 410 to second disc 425 via trunnions 420. More particularly, trunnions 420 may each contain a power roller portion 4205 that is configured to rotate in a predetermined direction and at a predetermined speed (e.g., first angular velocity coi ) about trunnion rotation axis 435. Power roller portion 4205 may be in simultaneous contact with both first disc 410 and second disc 425 at specific disc contact locations, as further described herein.

[0042] Trunnions 420 may be configured to pivot, or tilt, about a secondary axis (not illustrated) that is orthogonal to trunnion rotation axis 435. Tilting may cause an adjustment to a contact radius (represented in FIGS. 4A and 4B as R1 and R2) between trunnions 420 and first and second discs 410, 425. Stated differently, the disc contact locations that power roller portion 4205 of trunnions 420 contacts first disc 410 and second disc 425 at may change. This change may facilitate an RPM adjustment between first disc 410 and second disc 425, which correspondingly causes the second output shaft 430 to rotate faster or slower relative to first outputshaft 415, thereby enabling adjustment of the blade-crossing azimuth between the first and second sets of propeller blades. Once the azimuth is in the correct location, trunnions 420 may be rotated about trunnion rotation axis 435 to a position of equal contact radius with both first and second discs 410, 425, creating an equal and opposite RPM condition for both outputs.

[0043] As a non-limiting example of the adjustment process described above, FIG. 4A depicts an operating configuration of CVT traction drive system 400 in which second output shaft 430 is caused to rotate slower than inner output shaft 415. In this regard, trunnions 420 are oriented such that contact radius R1 with respect to first disc 410 is less than contact radius R2 with respect to second disc 425.Because the tangential velocity of trunnions 420 is constant at both contact points on first disc 410 and second disc 425, but the radius from the disc rotation axis is not equal (e.g., R1 is less than R2), second disc 425 will be caused to rotate at a slower RPM than first disc 410. In the converse example, illustrated in FIG. 4B, trunnions 420 may be tilted such that contact radius R1 with respect to first disc 410 is greater than contact radius R2 with respect to second disc 425, which may correspondingly cause second disc 425 to rotate faster than first disc 410.

[0044] In an aspect, a pilot of the aircraft may manually control the angling of trunnions 420 via inputs provided to a cockpit control systems. Additionally or alternatively, in another aspect, a computer system may dynamically control the angling of trunnions 420 to cause second disc 425 to speed up or slow down based upon a detected need as based upon received flight information.

[0045] In an aspect, any of the differential systems described above may additionally be used to optimize rotor stoppage / stowage. More particularly, any of the foregoing differential systems may be leveraged to align a first set of propeller bladesin a particular orientation with respect to a second set of propeller blades. Optimal propeller blade alignment during transport and / or storage may minimize the likelihood of damage occurring to the aircraft.

[0046] The many features and advantages of the present disclosure are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the present disclosure that fall within the true spirit and scope of the disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the present disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the present disclosure.

[0047] Moreover, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be used as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present disclosure. Accordingly, the claims are not to be considered as limited by the foregoing description.WHAT IS CLAIMED IS:1 . A drive system for an aircraft having a first set of propeller blades and a second set of propeller blades, the drive system comprising: a motor operably coupled to an input shaft at a first end of the input shaft, wherein operation of the motor is configured to cause the input shaft to rotate in a first direction at a first angular velocity; a first output shaft coupled to the input shaft at a second end portion of the input shaft, wherein the first output shaft is configured to rotate in the first direction at the first angular velocity; a second output shaft operatively coupled to the input shaft via a gear assembly including a plurality of gears, wherein the second output shaft is configured to rotate in a second direction, opposite the first direction, at the first angular velocity; and a cage component housing the gear assembly, wherein the cage component is configured to be rotatable about a central rotor axis; wherein rotation of the cage component is configured to cause the second output shaft to rotate at a second angular velocity, rotation of the second output shaft at the second angular velocity causing an adjustment in a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades.2. The drive system of claim 1 , wherein the first output shaft is coupled to the first set of propeller blades and wherein the second output shaft is coupled to the second set of propeller blades.3. The drive system of claim 2, wherein rotation of the cage component relative to the central rotor axis causes the adjustment to the blade-crossing azimuth to occur between the first set of propeller blades and the second set of propeller blades.4. The drive system of claim 1 , wherein the plurality of gears include: a first gear connected to a set of second gears; and a third gear connected to the set of second gears; wherein the set of second gears are positioned between the first gear and the third gear.5. The drive system of claim 4, wherein the first gear and the third gear have an equivalent number of gear teeth.6. The drive system of claim 4, wherein each gear of the set of second gears is a planetary gear.7. The drive system of claim 1 , further comprising a fourth gear coupled to the cage component, wherein actuation of the fourth gear causes the cage component to rotate about the central rotor axis.8. The drive system of claim 7, wherein the fourth gear is a worm gear.9. The drive system of claim 7, wherein actuation of the fourth gear is facilitated by a solenoid coupled to the fourth gear.10. An aircraft, comprising: a first set of propeller blades; a second set of propeller blades; and a drive system, including: a motor operably coupled to an input shaft; a first output shaft connected to the input shaft and to the first set of propeller blades; a second output shaft operatively coupled to the input shaft via a plurality of gears and to the second set of propeller blades; and a cage component that houses the plurality of gears, wherein the cage com ponent is configured to rotate about a central rotor axis and wherein rotation of the cage component causes an adjustment to an angular velocity at which the second set of propeller blades spin, wherein the adjustment tothe angular velocity adjusts a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades from a first position to a second position.11. The aircraft of claim 10, wherein the aircraft is an electric vertical take-off and landing vehicle.12. The aircraft of claim 10, wherein: the motor and the first set of propeller blades are rotatably coupled together by the input shaft; and the motor and the second set of propeller blades are rotatably coupled together by the plurality of gears.13. The aircraft of claim 10, wherein the first set of propeller blades are contra-rotating with respect to the second set of propeller blades about the central rotor axis.14. The aircraft of claim 10, wherein the drive system further includes a worm gear in mesh with the cage component and wherein rotation of the worm gear facilitates rotation of the cage component about the central rotor axis.15. The aircraft of claim 10, wherein a degree by which the cage component rotates is based on an input instruction provided to an actuator associated with the drive system.16. A method of adjusting a position of a blade-crossing azimuth at which a first set of propellers of an aircraft crosses a second set of propellers of the aircraft, com prising: receiving, at a differential drive system of the aircraft, an input to adjust an angular velocity at which the second set of propellers spin; controlling, using an actuator device, a cage component connected to the differential drive system to rotate by a predetermined amount based on the input; and adjusting, upon rotation of the cage component, the angular velocity of an output shaft connected to the second set of propellers.17. The method of claim 16, wherein the receiving the input comprises receiving a revolutions per minute (RPM) designation by which to adjust the angular velocity of the second set of propellers.18. The method of claim 16, wherein the controlling the cage component comprises actuating movement of a worm gear connected to the cage component.19. The method of claim 16, wherein the cage component houses a plurality of gears of a gear assembly and is rotatably coupled to the output shaft by the plurality of gears.20. The method of claim 19, wherein the plurality of gears include: a first gear connected to a set of second gears; and a third gear connected to the set of second gears; wherein the set of second gears are connected between the first gear and the third gear.DRIVE SYSTEM UTILIZING A DIFFERENTIAL FOR PHASE OPTIMIZED CONTRA-ROTATING COAXIAL ROTORS AND METHODS THEREOFCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 617,252, filed January 3, 2024, which is incorporated by reference herein in its entirety.FIELD OF THE DISCLOSURE

[0002] The present disclosure relates generally to embodiments of a drive system that utilize a differential gear set for splitting power into two contra-rotating outputs, and, more specifically, to a drive system that enables the control and optimization of the blade crossing azimuth in contra rotating propellers by adjusting characteristics of the differential gear set.BACKGROUND

[0003] Differential gear sets have been extensively utilized in the aircraft and marine industries in contra-rotating propeller systems. These gear sets enable the conversion of a single power input shaft into two concentric outputs with opposite rotation. Conventionally, differential gear sets have been employed in static configurations, whereby the cage portion of the differential is rigidly fixed to a structure of the propeller assembly. In this configuration, the azimuth of the contra rotating propellers is typically fixed at a predetermined location. Adjusting theazimuth typically requires disassembly and repositioning of various shafts and gears in the drive system, which may be time-consuming and burdensome.

[0004] The present disclosure is accordingly directed to an improved vehicle drive system that employs a rotating cage portion that houses the differential gear set. Rotation of the cage portion enables adjustment and optimization of the bladecrossing azimuth between a set of contra-rotating propellers without requiring manual user intervention. The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art, or suggestions of the prior art, by inclusion in this section.SUMMARY OF THE DISCLOSURE

[0005] According to certain aspects of the disclosure, systems and methods are disclosed for an adjustable differential gear set of a vehicle drive system.

[0006] In one aspect, a drive system is provided. The drive system may include a motor operably coupled to an input shaft at a first end, wherein operation of the motor is configured to cause the input shaft to rotate in a first direction at a first angular velocity. The drive system may further include a first output shaft coupled to the input shaft at a second end of the input shaft, wherein the first output shaft is configured to rotate in the first direction at the first angular velocity. The drive system may further include a second output shaft operatively coupled to the input shaft via a gear assembly including a plurality of gears, wherein the second output shaft is configured to rotate in a second direction, opposite the first direction, at the first angular velocity. The drive system may further include a cage component housing2the gear assembly, wherein the cage component is configured to be rotatable about a central rotor axis and wherein rotation of the cage com ponent is configured to cause the second output shaft to rotate at a second angular velocity and wherein rotation of the second output shaft at the second angular velocity causes an adjustment in a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades.

[0007] In another aspect, an aircraft is provided. The aircraft may include a first set of propeller blades. The aircraft may further include a second set of propeller blades. The aircraft may further include a drive system that includes: a motor operably coupled to an input shaft; a first output shaft connected to the input shaft and to the first set of propeller blades; a second output shaft operatively coupled to the input shaft via a plurality of gears and to the second set of propeller blades; and a cage component that houses the plurality of gears. The cage component of the drive system may be configured to rotate about a central rotor axis and wherein rotation of the cage component causes an adjustment to an angular velocity at which the second set of propeller blades spin, wherein the adjustment to the angular velocity adjusts a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades from a first position to a second position.

[0008] In yet another aspect, a method of adjusting a position of a bladecrossing azimuth at which a first set of propellers of an aircraft crosses a second set of propellers is disclosed. The method includes: receiving, at a differential drive system of the aircraft, an input to adjust an angular velocity at which the second set of propellers spin. The method further includes controlling, using an actuator device, a cage component connected to the differential drive system to rotate by a predetermined amount based on the input. The method further includes adjusting,3upon rotation of the cage component, the angular velocity of an output shaft connected to the second set of propellers.

[0009] Additional objects and advantages of the disclosed embodiments will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the disclosed embodiments. The objects and advantages of the disclosed embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments, as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the disclosed embodiments, and together with the description, serve to explain the principles of the disclosed embodiments. There are many aspects and embodiments described herein. Those of ordinary skill in the art will readily recognize that the features of a particular aspect or embodiment may be used in conjunction with the features of any or all of the other aspects or embodiments described in this disclosure. In the drawings:

[0012] FIG. 1A depicts a geared differential drive system in a fixed cage position, according to various aspects of the present disclosure.

[0013] FIG. 1 B depicts the geared differential drive system in a rotated cage position, according to various aspects of the present disclosure.4

[0014] FIG. 2A depicts an overhead view of a set of contra-rotating propeller blades with an indication of a first blade-crossing azimuth position, according to various aspects of the present disclosure.

[0015] FIG. 2B depicts the set of contra-rotating propeller blades in FIG. 2A in a crossed state at the first blade-crossing azimuth position, according to various aspects of the present disclosure.

[0016] FIGS. 3A depicts an overhead view of the set of contra-rotating propeller blades in FIG. 2A with an indication of a second blade-crossing azimuth position, according to various aspects of the present disclosure.

[0017] FIG. 3B depicts the set of contra-rotating propeller blades in FIG. 3A in a crossed state at the second blade-crossing azimuth position, according to various aspects of the present disclosure.

[0018] FIG. 4A depicts a friction-based differential drive system in a first configuration, according to various aspects of the present disclosure.

[0019] FIG. 4B depicts the friction-based differential drive system in a second configuration, according to various aspects of the present disclosure.DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0020] The terminology used below may be interpreted in its broadest reasonable manner, even though it is being used in conjunction with a detailed description of certain specific examples of the present disclosure. Indeed, certain terms may even be emphasized below; however, any terminology intended to be interpreted in any restricted manner will be overtly and specifically defined as such in this Detailed Description section. Both the foregoing general description and the5following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed.

[0021] In this disclosure, the term “based on” means “based at least in part on.” The singular forms “a,” “an,” and “the” include plural referents unless the context dictates otherwise. The term “exemplary” is used in the sense of “example” rather than “ideal.” The terms “comprises,” “comprising,” “includes,” “including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, or product that comprises a list of elements does not necessarily include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. Relative terms, such as, “substantially” and “generally,” are used to indicate a possible variation of ±10% of a stated or understood value.

[0022] Embodiments of the present disclosure may be incorporated into an aircraft. As used herein, “aircraft” may refer to an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, vessel, or virtually any other vehicle moving, or capable of moving, through air. Some non-limiting examples may include a helicopter, an airship, a hot air balloon, a vertical take-off craft (e.g., an electric vertical take-off and landing (eVTOL)), an unmanned aerial vehicle, or a drone.

[0023] Vehicles employing propeller systems are commonly used to transport people and / or objects from one location to another. Some propeller systems utilize two coaxial rotors in which one rotor is mounted above the other and each rotor is coupled to a set of propeller blades. The two rotors may be configured to contrarotate (i.e. , rotate in opposite directions around the same axis). The presence and utilization of the two coaxial rotors negates the need for a tail rotor and provides6symmetry of forces around the central axis during vehicle liftoff and during lateral movement in flight. Vehicles outfit with coaxial rotors also tend to be able to handle an increased payload, produce less noise, and may be designed to be more compact than single rotor vehicles in order to operate in areas where space is at a premium (e.g., the decks of ships, etc.).

[0024] When properly aligned with the inflowing airstream, the contra-rotation of the propellers produces equal and opposite hub moments that cancel out, which correspondingly prevents potentially harmful vibratory loads from being passed onto the vehicle airframe. Larger vibrations, however, may be created and passed to the airframe when unequal and non-opposite hub moments are created (e.g., when the inflowing air is no longer in proper alignment with the azimuth location of the propeller blades). In order to handle these larger vibrations, the weight of the propeller system and / or the vehicle airframe needs to be increased, which may correspondingly increase the rate of fuel consumption and generate higher operating costs.

[0025] Conventionally, differential gear sets have been utilized to transmit power from an engine to the coaxial rotor pair. A cage portion of the differential gear set is typically rigidly fixed, thereby locking the blade crossing azimuth of the propellers at a specific location. In these conventional configurations, adjustment of the azimuth location could only be achieved by disassembling and repositioning components (e.g., gears, shafts, etc.) of the differential gear set, which may be timeconsuming and burdensome. Additionally, these conventional restrictions prevent substantially real-time adjustment and optimization of the azimuth location to adapt to varying flight conditions. More particularly, because the inflow angle of an airstream with respect to the propellers varies with the direction of flight and / or the7prevailing winds, it is necessary for the aircraft to actively manage the azimuth location during certain portions of flight (e.g., during lift rotor operation). A need therefore exists for a simple, mechanical mechanism that is capable of substantially real-time azimuth control between the contra-rotating propellers.

[0026] Accordingly, the present disclosure provides a novel drive assembly that is capable of real-time azimuth control and optimization within contra-rotating propeller systems. More particularly, the novel assembly may be leveraged to produce variations in the revolutions per minute (RPM) between the coaxial rotors to change the azimuth location of the blade passage to align with the inflow of the airstream. By enabling precise azimuth adjustments without the need for gear set disassembly or repositioning, the novel assembly empowers users and / or aircraft systems to control the azimuth location in substantially real-time. This level of control may enable adjustments to be made to the propeller system to account for the vibratory forces that may be incurred during a variety of different operating conditions. Furthermore, the presence of real-time azimuth control may also enable lighter vehicle designs to be employed, which may be more operationally efficient.

[0027] The subject matter of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments. An embodiment or implementation described herein as “exemplary” is not to be construed as preferred or advantageous, for example, over other embodiments or implementations; rather, it is intended to reflect or indicate that the embodiment(s) is / are “example” embodiment(s). Subject matter may be embodied in a variety of different forms and, therefore, covered or claimed subject matter is intended to be construed as not being limited to any exemplary embodiments set forth herein;8exemplary embodiments are provided merely to be illustrative. Likewise, a reasonably broad scope for claimed or covered subject matter is intended. Among other things, for example, subject matter may be embodied as methods, devices, components, or systems. The following detailed description is, therefore, not intended to be taken in a limiting sense.

[0028] Throughout the specification and claims, terms may have nuanced meanings suggested or implied in context beyond an explicitly stated meaning. Likewise, the phrase “in one embodiment” or “in some embodiments,” or “in one aspect” or “in some aspects” as used herein does not necessarily refer to the same embodiment or aspect, and the phrase “in another embodiment” or “in another aspect” as used herein does not necessarily refer to a different embodiment or aspect. It is intended, for example, that claimed subject matter include combinations of exemplary embodiments in whole or in part.

[0029] Referring to FIG. 1A, first differential drive system 100 is illustrated according to one or more aspects of the present disclosure. In an aspect, first differential drive system 100 may be configured to split power from an input source (e.g., an electric motor) into two co-axial, contra-rotating outputs of equal and opposite RPM, i.e. , first output shaft 105 (e.g., an “inner output shaft”) and second output shaft 110 (e.g., an “outer output shaft”). Input shaft 115 may be operatively coupled to the motor 120 at first end 125 that causes input shaft 115 to rotate in a first direction at angular velocity coi . Inner output shaft 105 may be integrally coupled to input shaft 115 at second end 130, opposite first end 125, and may therefore always also rotate in the first direction and at the same angular velocity coi as input shaft 115.9

[0030] Outer output shaft 110 may be caused to rotate in a second direction, opposite the first direction, at angular velocity - coi , using power received from input shaft 115 through a particular differential gear path. More particularly, rotation of input shaft 115 may cause first gear 135 to rotate (rotation from right to left being shown in FIG. 1A). Second gears 140A, OB may be connected to first gear 135 and may be caused to rotate in opposite directions with respect to one another via rotation of first gear 135. In one aspect, second gears 140A, MOB may be planetary gears. The rotation of second gears 140A, MOB may cause third gear 145 to rotate, which may correspondingly facilitate the rotation of outer output shaft 110. In an aspect, first gear 135 may have an equivalent number of gear teeth as third gear 145.

[0031] First differential drive system 100 may further include differential cage 150 that is mounted around the gear path / assembly in a way that allows rotation of differential cage 150 about the central rotor axis. Gears 140A and MOB are attached to differential cage 150 via bearings. Differential cage 150 may be in mesh with fourth gear 160 (e.g., a worm gear) that, when fixed in place, fixes the blade-crossing azimuth (i.e. , the position at which a first set of propeller blades crosses a second set of propeller blades) of the two coaxial rotors in a set location. More particularly, because first gear 135 and third gear 145 each have equal tooth numbers, second gears 140A, MOB may act as idlers and enable inner output shaft 105 and outer output shaft 110 to rotate in opposite directions at equal RPM, thereby splitting the input power equally between the outputs (ignoring frictional losses). In this state, when the blade-crossing azimuth is properly aligned with the inflowing airstream, rotation of the first and second set of propeller blades associated with inner output shaft 105 and outer output shaft 110, respectively, create equal and opposite hub10moments that are resolved between output shaft bearings 155 and do not pass any vibratory loads into the airframe structure.

[0032] During flight, the vehicle may perform various maneuvers that cause the blade-crossing azimuth to no longer be in proper alignment with the inflow of air. In these situations, a user of the vehicle (e.g., a pilot) or an automated control system may provide inputs that cause differential drive system 100 to create a differential speed (e.g., as measured in revolutions per minute or “RPM’) between inner output shaft 105 and outer output shaft 110. This RPM differential may change the angular position of the blade crossing azimuth to a desired position, e.g., a position in which the azimuth is again in alignment with the inflowing airstream. To facilitate this change, in one aspect, an RPM input may be provided to differential cage 150 by actuating fourth gear 160. Actuation of fourth gear 160 may be facilitated by utilization of an actuation device, e.g., a solenoid, a cable system, etc. Actuated fourth gear 160 may cause differential cage 150 to rotate in the second direction (rotation from left to right being shown in FIB. 1 B) by a desired angular velocity C02, as shown in FIG. 1 B.

[0033] The cage rotation correspondingly creates a differential speed (e.g., RPM) between inner output shaft 105 and outer output shaft 110, as shown in FIG. 1 B. More particularly, although inner output shaft 105 maintains angular velocity coi , rotation of differential cage 150 in the second direction (i.e., in the same direction as outer output shaft 110) by angular velocity C02 causes outer output shaft 110 to rotate at an increased angular velocity of -wi + 2(co2). This change in angular velocity may enable a user to establish any desired azimuth position (e.g., based on operating and / or weather conditions). Once the azimuth is set at the desired position, differential cage 150 may be locked and the RPM input to fourth gear 160 may be11reversed. More particularly, fourth gear 160 may be caused to drive backward, thereby returning inner output shaft 105 and outer output shaft 110 to their initial operating state of equal and opposite RPMs.

[0034] In an aspect, vehicle control system 170 may receive input 165 from one or more sources. For instance, in one aspect, the pilot of the vehicle may manually control when an RPM input is provided to differential cage 150 and may also designate the exact value of the input (e.g., via interaction with various control components such as buttons, switches, handles, digital inputs, etc.). In another aspect, input 165 may be dynamically provided to control system 170. For instance, data may be captured by one or more vehicle sensors (e.g., wind speed, wind direction, propeller alignment with respect to wind direction, etc.) and may be transmitted to control system 170, e.g., in substantially real time. Control system 170 may process the received data and dynamically determine whether an adjustment should be made to the blade-crossing azimuth position and the degree to which the adjustment should be implemented. Additionally or alternatively, the control system 170 may be configured to implement azimuth adjustments in response to predetermined events and / or at predetermined points during flight (e.g., during liftoff, during flight direction change, etc.). In an aspect, control system 170 may transmit instructions to actuator 175, which may subsequently control rotation of fourth gear 160 based on an input designation. In an aspect, only minor RPM inputs need to be applied to differential cage 150 to facilitate meaningful azimuth adjustments. For instance, a baseline RPM of output shafts 105, 110 may be approximately 1000RPMs. To institute a 45 degree azimuth adjustment, only a 10 - 15 RPM input needs to be applied to differential cage 150.12

[0035] Although illustrated in FIGS. 1A and 1 B as being driven by a worm gear (i.e., fourth gear 160), such a designation is not limiting and differential cage150 may be actuated by another component. More particularly, fourth gear 160 may be replaced with any other mechanism to rotate differential cage 150, such as a spur, bevel, or face gear drive, cables, rotary actuators, etc. Additionally, the types of gears utilized in the gear assembly may also vary based upon a desired design configuration.

[0036] Other forms of differential gear systems may be utilized to achieve the same outcome as accomplished by first differential drive system 100. For instance, spur, face gear, or epicyclic differentials may be utilized in place of the bevel differential. Spur and face gear differentials may function the same as the bevel configuration when rotating the differential cage. Additional gearing stages may also be integrated into the differential assembly to provide an RPM reduction from the input to both outputs, thereby allowing for a smaller and more compact primary driver. It is important to emphasize, however, that although characteristics between the possible gearing systems may vary, each viable gearing system may contain a capability to implement a differential to at least one set of propeller blades to facilitate a blade-crossing azimuth adjustment.

[0037] Referring collectively to FIGS. 2A and 2B and FIGS. 3A and 3B, a nonlimiting example illustration of the adjustment of the blade-crossing azimuth position between a first and second set of propeller blades is provided. In FIG. 2A, first set of propeller blades 205 and second set of propeller blades 210 are shown to be contrarotating, e.g., rotating in opposite directions on a single axis as indicated by the directional arrows. At an original position, the blade-crossing azimuth may occur at position P1. More particularly, the blades of first set of propeller blades 205 and13second set of propeller blades 210 cross at position P1 , as depicted in FIG. 2B.When the blade-crossing azimuth position of first and second set of propeller blades205, 210 is aligned with incoming wind flow 215 (e.g., the crossed position of propeller blades is oriented perpendicular to incoming wind flow 215), the vibratory loads experienced by the aircraft are reduced.

[0038] Referring now to FIGS. 3A and 3B, in situations where the direction of incoming wind flow 215 changes (e.g., as a result of changing weather conditions, aircraft maneuvers, etc.), the blade-crossing azimuth position of first and second set of propeller blades 205, 210 may be adjusted in-flight to account for this change. For instance, FIGS. 3A and 3B illustrate that incoming wind flow 215 has changed direction relative to the direction depicted in FIGS. 2A and 2B. Inputs may be provided to a differential drive system to adjust the rotational speed of at least one of first or second set of propeller blades 205, 210 so that the blade-crossing azimuth position changes, e.g., to position P2, to align with the new incoming wind direction.

[0039] Referring collectively to FIG. 4A and 4B, a non-limiting example of a continuously variable transmission (CVT) traction drive system 400 is illustrated according to one or more aspects of the present disclosure. CVT traction drive system 400 is another potential system that may be leveraged to facilitate adjustments to a blade-crossing azimuth between aircraft propellers during flight. Unlike first differential drive system 100, CVT traction drive system 400 may facilitate azimuth adjustments without the utilization of a gear assembly. More particularly, CVT drive system 400 may be a “friction drive” system 400 with no gear teeth or mechanical locking mechanisms, as further described herein.

[0040] In an aspect, input shaft 405 may be operatively connected to a motor 402 at a first end of input shaft 405 that causes input shaft 405 to rotate in a first14direction at a first angular velocity coi . First disc 410 (e.g., a “primary” or “input disc”) may be integrally coupled to input shaft 405 and may correspondingly be caused to rotate in the first direction at the first angular velocity coi when first input shaft 405 is caused to rotate. First output shaft 415 (which may be connected to a first set of propeller blades (not illustrated)) may be integrally coupled to input shaft 405 at a second end of input shaft 405, opposite the first end of shaft 405, and may therefore always also rotate in the first direction at the first angular velocity coi .

[0041] One or more trunnions 420 may be positioned between first disc 410 and second disc 425 (e.g., a “secondary” or “output disc”) and second disc 425 may itself be connected to and facilitate the rotation of second output shaft 430 (which may be connected to a second set of propeller blades (not illustrated)). In an aspect, torque may be transferred from first disc 410 to second disc 425 via trunnions 420. More particularly, trunnions 420 may each contain a power roller portion 4205 that is configured to rotate in a predetermined direction and at a predetermined speed (e.g., first angular velocity coi ) about trunnion rotation axis 435. Power roller portion 4205 may be in simultaneous contact with both first disc 410 and second disc 425 at specific disc contact locations, as further described herein.

[0042] Trunnions 420 may be configured to pivot, or tilt, about a secondary axis (not illustrated) that is orthogonal to trunnion rotation axis 435. Tilting may cause an adjustment to a contact radius (represented in FIGS. 4A and 4B as R1 and R2) between trunnions 420 and first and second discs 410, 425. Stated differently, the disc contact locations that power roller portion 4205 of trunnions 420 contacts first disc 410 and second disc 425 at may change. This change may facilitate an RPM adjustment between first disc 410 and second disc 425, which correspondingly causes the second output shaft 430 to rotate faster or slower relative to first output15shaft 415, thereby enabling adjustment of the blade-crossing azimuth between the first and second sets of propeller blades. Once the azimuth is in the correct location, trunnions 420 may be rotated about trunnion rotation axis 435 to a position of equal contact radius with both first and second discs 410, 425, creating an equal and opposite RPM condition for both outputs.

[0043] As a non-limiting example of the adjustment process described above, FIG. 4A depicts an operating configuration of CVT traction drive system 400 in which second output shaft 430 is caused to rotate slower than inner output shaft 415. In this regard, trunnions 420 are oriented such that contact radius R1 with respect to first disc 410 is less than contact radius R2 with respect to second disc 425.Because the tangential velocity of trunnions 420 is constant at both contact points on first disc 410 and second disc 425, but the radius from the disc rotation axis is not equal (e.g., R1 is less than R2), second disc 425 will be caused to rotate at a slower RPM than first disc 410. In the converse example, illustrated in FIG. 4B, trunnions 420 may be tilted such that contact radius R1 with respect to first disc 410 is greater than contact radius R2 with respect to second disc 425, which may correspondingly cause second disc 425 to rotate faster than first disc 410.

[0044] In an aspect, a pilot of the aircraft may manually control the angling of trunnions 420 via inputs provided to a cockpit control systems. Additionally or alternatively, in another aspect, a computer system may dynamically control the angling of trunnions 420 to cause second disc 425 to speed up or slow down based upon a detected need as based upon received flight information.

[0045] In an aspect, any of the differential systems described above may additionally be used to optimize rotor stoppage / stowage. More particularly, any of the foregoing differential systems may be leveraged to align a first set of propeller blades16in a particular orientation with respect to a second set of propeller blades. Optimal propeller blade alignment during transport and / or storage may minimize the likelihood of damage occurring to the aircraft.

[0046] The many features and advantages of the present disclosure are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the present disclosure that fall within the true spirit and scope of the disclosure. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the present disclosure to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the present disclosure.

[0047] Moreover, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be used as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present disclosure. Accordingly, the claims are not to be considered as limited by the foregoing description.17

Claims

WHAT IS CLAIMED IS:1 . A drive system for an aircraft having a first set of propeller blades and a second set of propeller blades, the drive system comprising: a motor operably coupled to an input shaft at a first end of the input shaft, wherein operation of the motor is configured to cause the input shaft to rotate in a first direction at a first angular velocity; a first output shaft coupled to the input shaft at a second end portion of the input shaft, wherein the first output shaft is configured to rotate in the first direction at the first angular velocity; a second output shaft operatively coupled to the input shaft via a gear assembly including a plurality of gears, wherein the second output shaft is configured to rotate in a second direction, opposite the first direction, at the first angular velocity; and a cage component housing the gear assembly, wherein the cage component is configured to be rotatable about a central rotor axis; wherein rotation of the cage component is configured to cause the second output shaft to rotate at a second angular velocity, rotation of the second output shaft at the second angular velocity causing an adjustment in a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades.

2. The drive system of claim 1 , wherein the first output shaft is coupled to the first set of propeller blades and wherein the second output shaft is coupled to the second set of propeller blades.

3. The drive system of claim 2, wherein rotation of the cage component relative to the central rotor axis causes the adjustment to the blade-crossing azimuth to occur between the first set of propeller blades and the second set of propeller blades.

4. The drive system of claim 1 , wherein the plurality of gears include: a first gear connected to a set of second gears; and a third gear connected to the set of second gears; wherein the set of second gears are positioned between the first gear and the third gear.

5. The drive system of claim 4, wherein the first gear and the third gear have an equivalent number of gear teeth.

6. The drive system of claim 4, wherein each gear of the set of second gears is a planetary gear.

7. The drive system of claim 1 , further comprising a fourth gear coupled to the cage component, wherein actuation of the fourth gear causes the cage component to rotate about the central rotor axis.

8. The drive system of claim 7, wherein the fourth gear is a worm gear.

9. The drive system of claim 7, wherein actuation of the fourth gear is facilitated by a solenoid coupled to the fourth gear.

10. An aircraft, comprising: a first set of propeller blades; a second set of propeller blades; and a drive system, including: a motor operably coupled to an input shaft; a first output shaft connected to the input shaft and to the first set of propeller blades; a second output shaft operatively coupled to the input shaft via a plurality of gears and to the second set of propeller blades; and a cage component that houses the plurality of gears, wherein the cage com ponent is configured to rotate about a central rotor axis and wherein rotation of the cage component causes an adjustment to an angular velocity at which the second set of propeller blades spin, wherein the adjustment tothe angular velocity adjusts a blade-crossing azimuth at which the first set of propeller blades crosses the second set of propeller blades from a first position to a second position.

11. The aircraft of claim 10, wherein the aircraft is an electric vertical take-off and landing vehicle.

12. The aircraft of claim 10, wherein: the motor and the first set of propeller blades are rotatably coupled together by the input shaft; and the motor and the second set of propeller blades are rotatably coupled together by the plurality of gears.

13. The aircraft of claim 10, wherein the first set of propeller blades are contra-rotating with respect to the second set of propeller blades about the central rotor axis.

14. The aircraft of claim 10, wherein the drive system further includes a worm gear in mesh with the cage component and wherein rotation of the worm gear facilitates rotation of the cage component about the central rotor axis.2115. The aircraft of claim 10, wherein a degree by which the cage component rotates is based on an input instruction provided to an actuator associated with the drive system.

16. A method of adjusting a position of a blade-crossing azimuth at which a first set of propellers of an aircraft crosses a second set of propellers of the aircraft, com prising: receiving, at a differential drive system of the aircraft, an input to adjust an angular velocity at which the second set of propellers spin; controlling, using an actuator device, a cage component connected to the differential drive system to rotate by a predetermined amount based on the input; and adjusting, upon rotation of the cage component, the angular velocity of an output shaft connected to the second set of propellers.

17. The method of claim 16, wherein the receiving the input comprises receiving a revolutions per minute (RPM) designation by which to adjust the angular velocity of the second set of propellers.

18. The method of claim 16, wherein the controlling the cage component comprises actuating movement of a worm gear connected to the cage component.2219. The method of claim 16, wherein the cage component houses a plurality of gears of a gear assembly and is rotatably coupled to the output shaft by the plurality of gears.

20. The method of claim 19, wherein the plurality of gears include: a first gear connected to a set of second gears; and a third gear connected to the set of second gears; wherein the set of second gears are connected between the first gear and the third gear.23

Images