Rotor for a hover-capable aircraft

Abstract

A rotor for an aircraft is described, having a main shaft, a damping device for attenuating the transmission of vibrations from the main shaft in a plane orthogonal to a first axis, and a transmission device interposed between the main shaft and the damping device; the damping device comprises a first and a second mass unit having a first and a second mass rotatable about a first axis at a first and a second rotation speed, two control units operable to cause additional rotation of at least one of the first and second masses, and a first and a second support assembly carrying the first and second masses; each control unit controls the angle between the first and second masses and comprises a set of drive toothing integral with the first support assembly, a cogwheel having a set of control toothing meshing with the drive toothing, and an actuator rotating the cogwheel about a second axis and the first mass about the first axis.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to European Patent Application No. 19187420.5, filed on July 19, 2019, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a rotor for a hovering aircraft, and more particularly to a rotor for a helicopter. Background Technology

[0004] A helicopter is generally known to consist of a fuselage, a main rotor located at the top of the fuselage and capable of rotating about its own axis, and a tail rotor located at the end of the fuselage.

[0005] More specifically, the rotor basically includes: a hub that is rotatable about the aforementioned axis and equipped with multiple blades radially fastened to and protruding therefrom; and a main shaft that is connectable to a drive member and operatively connected to the hub to drive its rotation.

[0006] During operation, the rotor generates both high-frequency and low-frequency vibrations. More specifically, the low-frequency vibrations are generated by the downwash flow, which is separated from the blades and hub center. This separation occurs at the hub center and affects all vertical and horizontal aerodynamic surfaces of the tail and tail rotor.

[0007] During use, the high angular velocity rotation of the propeller blades generates additional high-frequency vibrations, which are transmitted to the main shaft and thus to the fuselage, thereby reducing the comfort of the occupants inside the fuselage.

[0008] More specifically, the vibration load acts axially and orthogonally to the axis of rotation of the main shaft on both the hub and the main shaft.

[0009] It is known in the industry that, in a rotating reference frame, the angular frequency of the vibration load acting in the rotor plane, thus integral with the rotor, hub, and main shaft, is equal to (N+1)*Ω, (N-1)*Ω, and their multiples, where Ω is the rotational speed of the main shaft and N represents the number of rotor blades. It is also known that, when transmitted from the rotating system to the fixed system of the fuselage, the vibration load acting in the rotor plane undergoes a frequency shift and has an angular frequency equal to N*Ω and its associated multiples in the fixed system.

[0010] Based on the foregoing, the industry clearly feels the need to limit the transmission of vibrations with the aforementioned angular frequency, which is equal to the product of the spindle speed and the number of rotor blades, from the spindle to the fuselage.

[0011] Therefore, passive attenuation devices and active attenuation devices are known.

[0012] Passive damping devices essentially consist of mass bodies elastically suspended from the main shaft or rotor hub. Vibrations of these suspended mass bodies can at least partially dissipate vibrations on the main shaft and rotor hub.

[0013] Although they are easy to build and install and do not require external power sources from the rotor, passive attenuation devices have the greatest limitations in terms of the performance they can provide.

[0014] Active damping devices are essentially actuators that apply damping forces on the rotor hub or main shaft to counteract the transmission of vibrations to the fuselage.

[0015] Examples of these active attenuation devices are shown in the applicant's patent application EP-A-3421358.

[0016] The patent application illustrates the use of damping devices to reduce the transmission of vibrations (e.g., bending vibrations), i.e., the transmission in a plane orthogonal to the axis of the main shaft.

[0017] More specifically, the attenuation device includes:

[0018] – A first mass element and a second mass element, each having a pair of mass bodies that can rotate eccentrically about the principal axis; and

[0019] - Two control units, which are associated with the corresponding mass units and are adapted to adjust the angle defined by the associated mass body.

[0020] The mass body is rotated and coupled to the main shaft by a transmission device, so that the mass body of the first mass unit rotates eccentrically around the main shaft relative to the fixed system in the same rotational direction as the main shaft at a rotational speed of N*Ω, and the mass body of the second mass unit rotates relative to the fixed system in the opposite rotational direction to the main shaft at a rotational speed of N*Ω.

[0021] In this way, the mass body generates a corresponding radial centrifugal force relative to the axis of the main shaft.

[0022] For the first mass element, the component of the centrifugal force in the plane orthogonal to the main axis varies sinusoidally with respect to the rotor at an angular frequency equal to (N-1)*Ω.

[0023] Conversely, for the second mass unit, the component of the second centrifugal force in the aforementioned plane varies sinusoidally with respect to the rotor at an angular frequency equal to (N+1)*Ω.

[0024] The vector sum of the centrifugal forces generated by the mass body of the first mass unit corresponds to the first attenuated resultant force.

[0025] The vector sum of the centrifugal forces generated by the mass body of the second mass unit corresponds to the second attenuated resultant force.

[0026] Each control unit can be operated to selectively adjust the angle of the corresponding mass body of the corresponding first or second mass unit relative to a fixed direction between (a plurality of) positions, thereby adjusting the magnitude and phase of the corresponding first and second damping resultant forces relative to the fixed direction.

[0027] For each mass body of the associated first or second mass unit, each control unit also includes:

[0028] - Electric motor;

[0029] - A worm gear, operably coupled to a corresponding electric motor and rotatable about a corresponding axis; and

[0030] - A gear that is coupled to a worm and operatively connected to a corresponding mass.

[0031] The operation of each electric motor causes the mass bodies of the first and second mass units to rotate additionally relative to the transmission device through the coupling between the associated worm and gear.

[0032] In this way, the magnitude and phase of the first and second resultant forces relative to a fixed direction can be adjusted.

[0033] Because of the high reduction ratio between the worm and the associated gear, the coupling between the worm and the associated gear requires the electric motor to generate a high torque value rapidly.

[0034] Furthermore, due to the irreversible coupling between the worm and the associated gear, known types of damping devices can only cause the mass to rotate additionally in one direction.

[0035] As a result, known types of damping devices can be improved in terms of flexibility and responsiveness in generating the first and second damping results, especially when the magnitude and direction of the vibration to be damped change rapidly.

[0036] In the event of a motor malfunction, the irreversibility of the coupling between the worm and the gear can also cause the damping device to lock up.

[0037] Furthermore, the attenuation device described in the aforementioned patent application EP-A-3421358 has a significant axial volume.

[0038] Therefore, the industry recognized the need to reduce vibrations transmitted to the fuselage as precisely and quickly as possible.

[0039] The industry also recognizes the need to reduce vibrations in the rotor plane, maintain the effectiveness of the aforementioned active damping devices, and minimize weight, volume, and total cost.

[0040] Finally, the industry recognized the need to limit the stresses acting on the transmission as much as possible in a plane orthogonal to the axis of rotation of the spindle, especially the stresses acting on the shafts, gears and bearings of the transmission.

[0041] GB1120193, US2014 / 360840, WO2015031768 and WO2015031768 describe known types of attenuation devices that utilize the centrifugal force of a mass body that can rotate eccentrically relative to the axis of rotation of the spindle.

[0042] US-B-9452828 discloses a vibration damper for an aircraft having at least one counterweight mounted in a rotating system of a rotor hub of the aircraft. Each counterweight is rotatable about the axis of rotation of the hub relative to the hub and each other counterweight. A drive mechanism is provided for rotating each counterweight about the axis of rotation at a selected speed to generate an oscillating shear force that counteracts and attenuates vibrations generated by the rotor at a selected frequency. The vertically oriented vibration damper is configured to counteract and attenuate oscillating forces generated by the vertical rotor, which would otherwise travel vertically along the rotor main shaft and enter the frame. The vibration damper has counterweights that rotate about separate axes offset from each other. Summary of the Invention

[0043] The object of the present invention is to produce a rotor for a hovering aircraft that can meet at least one of the requirements mentioned above in a simple and inexpensive manner.

[0044] The present invention achieves the above-mentioned objective in relation to the rotor of a hovering aircraft as defined in claim 1. Attached Figure Description

[0045] To better understand the invention, two preferred embodiments are described below by way of non-limiting example and with reference to the accompanying drawings, in which:

[0046] - Figure 1 This is a side view of a helicopter including a rotor according to the invention, wherein some parts have been removed for clarity;

[0047] - Figure 2 Along Figure 1 The section taken from line II-II shows the combination in Figure 1 The first embodiment of the attenuation device in the rotor, wherein some parts are omitted for clarity;

[0048] - Figure 3 A partial sectional view is shown. Figure 2 Some details of the attenuation device, with some parts omitted for clarity;

[0049] - Figure 4 A partial sectional view is shown. Figure 2 Some details of the second embodiment of the attenuation device, wherein some parts have been omitted for clarity;

[0050] - Figure 5 A partial sectional view is shown. Figure 4 Some details of the attenuation device, with some parts omitted for clarity; and

[0051] - Figure 6 It shows Figures 2 to 5 A schematic diagram of some components of the attenuation device. Detailed Implementation

[0052] Reference Figure 1 The attached figure, labeled 1, indicates an aircraft capable of hovering, particularly a helicopter.

[0053] Helicopter 1 includes:

[0054] -Fuse 2;

[0055] - Main rotor 3, which is positioned on top of fuselage 2 and can rotate about axis A; and

[0056] - A tail rotor (not shown and known in itself) is located at one end of the fuselage 2 and can rotate about its own axis transverse to axis A.

[0057] More specifically, the rotor 3 includes a hollow hub 4 with an axis A, which cantileveredly carries multiple blades 5 extending radially relative to the axis A.

[0058] Rotor 3 also includes main shaft 50 ( Figure 2 The main shaft 50 is angularly coupled to the rotor hub 4 in an integral manner and connected to the drive unit (e.g., turbine) of the helicopter 1 in a manner not shown. In particular, the rotor hub 4 is driven by the main shaft 50 to rotate about axis A.

[0059] In the example shown, the main shaft 50 is partially housed within the propeller hub 4.

[0060] Preferably, the main shaft 50 is hollow.

[0061] Special reference Figure 1 The rotor 3 also includes an airflow conveyor 6 adapted to guide the airflow generated by the rotation of the rotor 3 according to a predetermined path, which is configured to limit the vibration caused by the separation of the airflow from the blade tips of the blades 5 disposed at the end opposite to the hub 4.

[0062] Specifically, the airflow conveyor 6 is annular, extends around axis A, and is positioned on the opposite side of the rotor hub 4 relative to the fuselage 2.

[0063] Preferably, the airflow conveyor 6 has a “cap-like” shape and is defined by a pair of surfaces facing each other in the axial direction.

[0064] Preferably, the walls of the air conveyor 6 are shaped such that their axial distance gradually decreases in the radial direction starting from axis A.

[0065] The rotor 3 also includes a vibration damping device 7, which is configured to reduce the transmission of vibration to the main shaft, especially in the plane orthogonal to axis A. In other words, the vibration damping device 7 is configured to reduce the transmission of vibration to the fuselage 2 in the plane of the rotor disk.

[0066] The attenuation device 7 includes mass unit 8 and mass unit 9, which can rotate about axis A with a first angular velocity and a second angular velocity, respectively.

[0067] Mass units 8 and 9 are indirectly coupled to spindle 50.

[0068] Mass units 8 and 9 each include a corresponding mass body 10 and a corresponding mass body 11 that are eccentrically arranged relative to axis A and eccentrically rotatable about axis A.

[0069] Masses 10 and 11 of mass unit 8 are coupled to hub 4 and main shaft 50, so that they can rotate relative to main shaft 50 about axis A in the same direction as the rotation of main shaft about axis A, with an angular velocity equal to (N-1)*Ω, where N is the number of blades 5 and Ω is the angular rotational speed of main shaft 50.

[0070] In this specification, the term angular frequency refers to frequency multiplied by 2π.

[0071] In a similar manner, the mass bodies 10 and 11 of mass unit 9 are coupled to the hub 4 and the main shaft 50, so that they can rotate relative to the main shaft 50 about axis A in the opposite direction to the rotation of the main shaft 50 about axis A with an angular velocity equal to (N+1)*Ω.

[0072] Unless otherwise specified, it should be understood in the following text of this specification that the angular velocities (N-1)*Ω and (N+1)*Ω are considered in a reference frame integral with the principal axis 50.

[0073] As they rotate around axis A, the respective mass bodies 10 and 11 of mass units 8 and 9 generate corresponding centrifugal forces that are radially directed relative to axis A and located in a plane orthogonal to axis A.

[0074] Each of these centrifugal forces has a corresponding component in the aforementioned plane orthogonal to axis A, and they have sinusoidal trajectories with angular frequencies corresponding to the angular velocities (N-1)*Ω and (N+1)*Ω of the corresponding masses 10 and 11 about axis A.

[0075] The vector sum of the centrifugal forces generated by the masses 10 and 11 of mass unit 8 corresponds to the first attenuated resultant force. The component of this first resultant force in a plane orthogonal to axis A has an angular frequency of (N-1)*Ω.

[0076] Thus, taking into account the transmission from the rotation system of rotor 3 to the fixed system of fuselage 2, the aforementioned component of the first damping resultant force is a sine curve with an angular frequency of N*Ω relative to a reference frame integral with fuselage 2.

[0077] The vector sum of the centrifugal forces generated by the masses 10 and 11 of mass unit 9 corresponds to the second attenuated resultant force. The component of this second resultant force in a plane orthogonal to axis A has an angular frequency of (N+1)*Ω.

[0078] Thus, taking into account the transmission from the rotation system of rotor 3 to the fixed system of fuselage 2, the aforementioned component of the second damping resultant force is a sine curve with an angular frequency of N*Ω relative to a reference frame integral with fuselage 2.

[0079] Specifically, the magnitudes of these first and second damping forces depend on the weights of the respective masses 10 and 11, the angles defined by the masses 10 and 11, and the corresponding rotational speeds around axis A.

[0080] In fact, for example, the magnitude of the first (second) damping resultant force is the largest when the angle between masses 10 and 11 is the smallest. Conversely, when the angle is 180 degrees, the magnitude of the first (second) damping resultant force is zero.

[0081] In other words, the magnitude of the first (second) resultant force can be adjusted by changing the relative angle between the mass bodies 10 and 11 of each mass unit 8 (9).

[0082] By uniformly changing the position of the mass bodies 10 and 11 of each mass unit 8 (9) relative to a fixed direction, the phase angle defined between the first (second) resultant force and the fixed direction in a plane orthogonal to axis A can be adjusted instead.

[0083] In the following description, the term "angle between mass bodies 10 and 11" refers to the angular distance between the line segments connecting axis A to the centroids of the respective mass bodies 10 and 11 in the radial direction of axis A.

[0084] In the example shown, the mass bodies 10 and 11 of mass elements 8 and 9 are identical to each other and are located at the same distance from axis A.

[0085] In the example shown, the mass bodies 10 and 11 of mass unit 8 are the same as those of mass body 10 and 11 of unit 9.

[0086] As a result, the centrifugal forces generated by the mass bodies 10 and 11 of mass unit 8 (9) are equal in magnitude.

[0087] Special reference Figure 2 The rotor 3 also includes a transmission unit 15, which is configured to transfer the rotation of the main shaft 50 about axis A to the attenuation device 7. Specifically, the transmission unit 15 is functionally inserted between the main shaft 50 and the mass units 8 and 9, and is configured to drive the corresponding masses 10 and 11 to rotate eccentrically about axis A in opposite directions of rotation with angular velocities of (N-1)*Ω and (N+1)*Ω relative to the main shaft 50, respectively.

[0088] Specifically, the transmission unit 15 is functionally connected to the main shaft 50 and the mass bodies 10 and 11 of the mass units 8 and 9.

[0089] Mass unit 8 is axially separated from mass unit 9. In particular, mass unit 8 is positioned above mass unit 9, or more precisely, mass unit 9 is inserted between mass unit 8 and transmission unit 15 and / or propeller hub 4.

[0090] In addition, the attenuation device 7 includes a housing 12, which houses the mass units 8 and 9 and a portion of the transmission unit 15.

[0091] Preferably, the housing 12 is inserted between the propeller hub 4 and the air conveyor 6. In particular, the air conveyor 6 at least partially covers the housing 12.

[0092] More specifically, the transmission unit 15 includes ( Figure 2 ):

[0093] - Auxiliary shaft 16, which is connected at an angle to mass element 8, particularly to the corresponding mass bodies 10 and 11, and is rotatable about axis A;

[0094] - Auxiliary shaft 17, which is connected at an angle to mass element 9, particularly to the corresponding masses 10 and 11, and is rotatable about axis A; and

[0095] - The conversion unit 18 is functionally coupled to the main shaft 50 and the auxiliary shafts 16 and 17, and is configured to receive motion with an angular velocity of Ω from the rotatable main shaft 50 and transfer that motion to the auxiliary shafts 16 and 17.

[0096] Thus, auxiliary shaft 16 and auxiliary shaft 17 rotate around axis A at a rotational speed of (N-1)*Ω in the same direction as the rotational direction of main shaft 50 and at a rotational speed of (N+1)*Ω in the opposite direction to the rotational direction of main shaft 50, respectively.

[0097] More specifically, the conversion unit 18 includes a first planetary gear train functionally inserted between the main shaft 50 and the auxiliary shaft 16, and a second planetary gear train functionally inserted between the main shaft 50 and the auxiliary shaft 17.

[0098] In particular, the first and second planetary gear trains are also operatively coupled to the main shaft 50.

[0099] In the example shown, it will be described in further detail that the second planetary gear train includes some parts of the first planetary gear train. This allows for the acquisition of the transmission unit 15, and more particularly, the compact conversion unit 18.

[0100] Preferably and particularly refer to Figure 2 The conversion unit 18 includes:

[0101] - A tubular housing 21 having teeth 22 located radially inward relative to axis A;

[0102] - Sun gear 23, which is rotatable about axis A, has teeth 24 located radially outward relative to axis A, and is integrally formed with auxiliary shaft 16 at an angle; and

[0103] - Multiple planetary gears 25 ( Figure 2 (Only one of them is shown in the figure), they are rotatable about their respective axes of rotation B and each has a corresponding first tooth 26 located radially outward relative to the respective axis B.

[0104] In the example shown, axis B is parallel to and deviates from axis A.

[0105] Specifically, each of the first gear teeth 26 meshes with gear teeth 22 and 24.

[0106] Specifically, planetary gear 25 is operatively and indirectly coupled to the main shaft 50 to be driven to rotate about axis A. Furthermore, planetary gear 25 rotates about a corresponding axis B due to the interaction between corresponding teeth 26 and 22. This rotation is then transferred to auxiliary shaft 16 via the meshing between teeth 26 and 24.

[0107] Specifically, the first planetary gear system includes a housing 21, a sun gear 23 and a planetary gear 25, as well as internal gear teeth 22, gear teeth 24 and gear teeth 26.

[0108] Preferably and particularly refer to Figure 2The conversion unit 18 also includes:

[0109] - Sun gear 28, which is rotatable about axis A, has teeth 29 located radially outward relative to axis A, and is integrally formed with auxiliary shaft 17 at an angle; and

[0110] - Multiple planetary gears 30 ( Figure 2 (Only one of them is shown in the figure), they are rotatable about their respective axes of rotation C (parallel to axis A), and each has a corresponding first tooth 31 and a corresponding second tooth 32 located radially outside the corresponding axis C.

[0111] In particular, each planetary gear 25 also includes a second tooth 33 located radially outward relative to the corresponding axis B.

[0112] Specifically, each set of first gear teeth 31 meshes with at least one set of corresponding second gear teeth 33, and each set of second gear teeth 32 meshes with gear teeth 29. Due to this configuration, each planetary gear 30 is driven to rotate by the rotation of the corresponding planetary gear 25, which in turn can rotate relative to the housing 21.

[0113] In the example shown, axis C is parallel to and deviates from axis A.

[0114] Specifically, the second planetary gear system includes a housing 21, at least a portion of a planetary gear 25, a planetary gear 30 and a sun gear 28, an inner gear 22, and gear teeth 26, 31, 32 and 33.

[0115] The dimensions of gear teeth 22, 24, 26, 31, 32 and 33 are set to enable auxiliary shaft 17 to achieve a rotational speed of (N+1)*Ω and auxiliary shaft 16 to achieve a rotational speed of (N-1)*Ω.

[0116] The transmission unit 15, and particularly the conversion unit 18, also includes a planetary gear carrier for supporting planetary gears 25 and 30 in a manner rotatable about corresponding axes B and C. Specifically, the planetary gear carrier is rotatable about axis A and is integrally formed with the main shaft 50 at an angle. In particular, due to the connection between the planetary gear carrier and the main shaft 50, the rotation of the planetary gear carrier about axis A is achieved when the main shaft 50 rotates about axis A.

[0117] Preferably, the planetary gear carrier includes a support base 34 orthogonal to axes A, B, and C, and a plurality of rotating shafts 35 parallel to the corresponding axes B and C. The rotating shafts 35 are fixed to the support base 34 and cantilevered over it.

[0118] Preferably, the support base 34 is operatively connected to the main shaft 50, so that it can be driven to rotate about axis A during use.

[0119] Preferably, the outer shell 21 is fixed to the housing 12.

[0120] Special reference Figure 2 and Figure 3 The attenuation device 7 also includes two control units 40, one of which is operatively connected to the mass unit 8 and the other is operatively connected to the mass unit 9.

[0121] More specifically, each control unit 40 can be operated to cause the mass bodies 10, 11 of the corresponding mass units 8, 9 to undergo additional rotation about axis A relative to the corresponding auxiliary axes 16, 17.

[0122] This rotation allows for the selective adjustment of the angle between the mass bodies 10 and 11 of the corresponding mass units 8 and 9, as well as the position of the mass bodies 10 and 11 relative to the fixed direction in which they rotate integrally with the corresponding auxiliary axes 16 and 17, while the mass units 8 and 9 rotate around axis A with corresponding first and second angular velocities ((N-1)*Ω and (N+1)*Ω).

[0123] In this way, each control unit 40 can selectively control the magnitude and corresponding phase of the corresponding first or second damping resultant force generated by the associated mass units 8, 9. Therefore, the vibrations originating from the propeller blades 5 and transmitted from the main shaft 50 to the fuselage can be reduced by utilizing the first and second damping resultant forces, which have desired magnitudes and directions, respectively.

[0124] Mass units 8 and 9 each include a corresponding support component 41 that carries the corresponding mass body 10 and a corresponding support component 42 that carries the corresponding mass body 11. Figure 2 and Figure 3 ).

[0125] More specifically, support components 41 and 42 are each coupled to transmission unit 15 and thus driven to rotate about axis A with corresponding first angular velocity (N-1)*Ω and second angular velocity (N+1)*Ω.

[0126] In particular, each of the support components 41 and 42 can also be selectively operated by the corresponding control unit 40 to perform additional rotation relative to the corresponding auxiliary shafts 16 and 17, and thus selectively adjust the angle between the mass bodies 10 and 11 of the corresponding mass units 8 and 9 and the position of the mass bodies 10 and 11 relative to a fixed direction.

[0127] Support components 41 and 42 each also include ( Figure 3 ):

[0128] -The corresponding annular support 44; and

[0129] - Arm 43, which cantilevered radially from axis A and carried the corresponding mass bodies 10 and 11.

[0130] In the example shown, support components 41 and 42 each extend coaxially with the corresponding auxiliary axis 16 or 17, and thus coaxially with axis A.

[0131] Specifically, each annular support 44 can rotate about a corresponding auxiliary axis 16 or 17 and is coupled to a corresponding control unit 40, thereby enabling adjustment of the relative angle between the corresponding mass bodies 10 and 11.

[0132] Mass units 8 and 9 each also include a corresponding base support 45, which is rotatable about axis A and operatively connected to transmission unit 15 to be driven to rotate about axis A at a first rotational speed (N-1)*Ω and a second rotational speed (N+1)*Ω, respectively. In particular, the base supports 45 of mass units 8 and 9 are integrally formed with and connected to the corresponding auxiliary shafts 16 or 17.

[0133] Support components 41 and 42 are each rotatably connected to the corresponding support base 45.

[0134] In this way, the motion is transferred from the corresponding auxiliary shafts 16 and 17 to the corresponding support components 41 and 42 and the corresponding mass bodies 10 and 11, respectively.

[0135] Specifically, support components 41 and 42 are each axially disposed on the first side of the base bracket 45 in a direction parallel to axis A.

[0136] Preferably, each base support 45 is made in the form of a circular plate.

[0137] Masses 10 and 11 each also include a corresponding wheel 46 that can rotate about the corresponding axis of rotation E.

[0138] Preferably, the masses 10 and 11 are each coupled to the corresponding support assembly 41 or 42, particularly the corresponding arm 43, in a manner that allows radial movement relative to axis A. In this way, the masses 10 and 11 are each pressed against the radial inner wall of the housing 12 by centrifugal force.

[0139] Due to this contact and the rotation of the masses 10 and 11 around axis A, each wheel 46 rotates around the corresponding axis E.

[0140] Furthermore, due to this contact between the wheel 46 and the inner wall of the housing 12, and due to the support system of the main shaft 50 relative to the housing 12, the corresponding centrifugal force is effectively transmitted to the main shaft 50.

[0141] Alternatively, mass bodies 10 and 11 may each include one or more wheels 46 rotatable about their respective axes of rotation E.

[0142] Masses 8 and 9, each with its own mass body 10 and corresponding mass body 11, lie on the same plane orthogonal to axis A. As a result, the dimensions of wheel 46 define the minimum angle between the respective mass bodies 10 and 11 that allows them to contact each other.

[0143] The mass bodies 10 and 11 of mass units 8 and 9 each also include a coupling element 47, which carries the corresponding wheel 46 and is coupled to the corresponding arm 43.

[0144] Masses 10 and 11 each also include a pin 48 parallel to axis A, which rotatably couples the corresponding wheel 46 to the corresponding coupling element 47 and defines the corresponding axis E.

[0145] Specifically, the corresponding wheel 46 can rotate about the corresponding pin 48 and about the associated axis E.

[0146] Each pin 48 is coupled to a corresponding coupling element 47 in a radially movable manner, so that the corresponding wheel 46 can move radially.

[0147] Specifically, each coupling element 47 includes two radially extending guide grooves 49 parallel to each other, in which corresponding ends of the corresponding pins 48 are received. In particular, each end can slide in the corresponding guide groove 49 under the action of centrifugal force to achieve radial movement of the corresponding pin 48, thereby achieving radial movement of the corresponding wheel 46.

[0148] Alternatively or additionally, each coupling element 47 is coupled to the corresponding arm 43 in a radially movable manner.

[0149] Advantageously, each control unit 40 includes ( Figure 3 ):

[0150] - Two sets of drive gear teeth 55, one set of which is integrated with the corresponding support component 41, and the other set of which is integrated with the corresponding support component 42;

[0151] - Two gears 56, each having a corresponding control tooth 57 meshing with a corresponding set of drive teeth 55 and rotatable about their own axis F, which is parallel to and offset from axis A; and

[0152] - Two actuators 58, in particular two electric motors, each connected to a corresponding gear 56, and operable to rotate the corresponding gear 56 about a corresponding axis F and to rotate the corresponding support assembly 41 or 42 about axis A.

[0153] Specifically, each drive gear tooth 55 and each set of control gear teeth 57 are made of self-lubricating materials and / or polymer materials.

[0154] Each control unit 40 also includes two annular elements 59, one connected to a corresponding support assembly 41 and the other connected to a corresponding support assembly 42. In particular, each annular element 59 has a corresponding drive gear tooth 55 on its circumferential edge.

[0155] Preferably, each annular element 59 and the corresponding drive gear tooth 55 are made as a single piece and / or made of the same material.

[0156] according to Figure 3 In the illustrated embodiment, each annular element 59 is fastened to a corresponding annular support 44. In particular, each annular element 59 is inserted at least between the corresponding annular support 44 and the corresponding base support 45.

[0157] Preferably, each annular element 59 connected to the corresponding support assembly 41 is inserted between the support base 34 and the corresponding annular element 59 connected to the corresponding support assembly 42.

[0158] according to Figure 3 In the embodiment shown, each set of drive gear teeth 55 is arranged radially outward relative to axis A.

[0159] In addition, each set of drive gear teeth 55 is arranged radially inward relative to the corresponding gear 56 about axis A.

[0160] Furthermore, the groups of drive gear teeth 55 overlap each other axially and are positioned at the same radial distance from axis A.

[0161] Each actuator 58 also includes an output shaft 60 rotatable about axis A, on which a corresponding gear 56 is mounted.

[0162] Each actuator 58 is configured to selectively rotate the corresponding gear 56 and the corresponding output shaft 60 in two possible directions.

[0163] Each actuator 58 is also fastened to a corresponding base bracket 45, specifically on the second side of the corresponding base bracket 45 opposite to the corresponding first side in a direction parallel to axis A.

[0164] Preferably, the mass bodies 10 and 11 are axially inserted between the actuator 58 of the mass unit 8 and the actuator 58 of the mass unit 9 along axis A. Figure 2 ).

[0165] In addition, the actuators 58 of mass units 8 and 9 are inserted radially between mass bodies 10 and 11.

[0166] This reduces the axial dimension of the housing 12.

[0167] The rotor 3 also includes a first slip ring and a second slip ring (not shown) to electrically connect the power source carried by the fuselage 2 to the corresponding actuator 58.

[0168] Rotor 3 also includes ( Figure 6 ):

[0169] - Multiple sensors 100, configured to generate multiple signals associated with the acceleration state of the fuselage 2 in a plane orthogonal to axis A; and

[0170] - Control unit 101 is configured to generate control signals for actuator 58 of control unit 40 based on signals generated by the aforementioned sensors.

[0171] In use, the main shaft 50 drives the hub 4 and blades 5 to rotate around axis A.

[0172] More specifically, the main shaft 50 rotates about axis A with an angular velocity Ω in a reference frame that is integrated with the fuselage 2.

[0173] The rotation of the hub 4 and blades 5 generates vibrations, which tend to be transmitted to the main shaft 50 and from there to the fuselage 2.

[0174] For the fixed system of fuselage 2, these vibrations mainly have an angular frequency equal to N*Ω, where N is the number of blades 5 and Ω is the angular rotational speed of the main shaft 50.

[0175] To reduce these vibrations, the main shaft 50 drives the corresponding mass bodies 10 and 11 of the mass units 8 and 9 to rotate eccentrically around axis A in the corresponding directions that are the same as and opposite to the rotation direction of the main shaft 50, respectively, via the transmission unit 15.

[0176] The rotation of the mass bodies 10 and 11 of mass units 8 and 9 generates corresponding centrifugal forces acting on the main shaft 50.

[0177] More specifically, the centrifugal forces generated by the mass bodies 10 and 11 of mass unit 8(9) have components in a plane orthogonal to axis A, and these components have sinusoidal trajectories and corresponding angular frequencies equal to (N-1)*Ω and (N+1)*Ω in a reference frame integral with the principal axis 50.

[0178] The first (second) attenuation resultant force generated by the mass bodies 10 and 11 of mass unit 8 is equal to the vector sum of the first (second) centrifugal forces.

[0179] The first and second damping forces weaken the transmission of vibrations to fuselage 2 in a plane orthogonal to axis A.

[0180] Furthermore, the combined effect of these first and second damping forces has an angular frequency equal to N*Ω in a reference frame integral with the fuselage 2, which is the angular frequency of the disturbance vibration force that is to be reduced.

[0181] Furthermore, the magnitude of these first and second damping forces depends on the angle between the corresponding masses 10 and 11 of the respective mass units 8 and 9. For example, the magnitude of the first and second damping forces is maximized when the angle defined between the associated masses 10 and 11 is minimized.

[0182] Conversely, when the angle between the associated masses 10 and 11 is 180 degrees, the magnitude of these first and second damping forces is minimal and equal to zero.

[0183] Conversely, the phase of the first and second damping forces relative to the fixed direction depends on the angular positions of the masses 10 and 11 relative to the fixed direction.

[0184] It is important to note that when the control unit 40, and especially the actuators 58, are activated and when they are deactivated, the mass bodies 10 and 11 apply corresponding first and second resultant forces on the main shaft 50 and rotate at corresponding angular velocities (N-1)*Ω and (N+1)*Ω.

[0185] However, selective activation of the control unit 40, particularly the actuator 58, can change the magnitude and phase of the first resultant force and the second resultant force on the spindle 50, thereby adjusting the magnitude and phase of the first damped resultant force and the second damped resultant force.

[0186] The function of rotor 3 is described below starting from the state where control unit 40, and especially actuator 58, is deactivated.

[0187] In this case, the relative angle between the corresponding mass bodies 10 and 11 is fixed.

[0188] The main shaft 50 drives the auxiliary shafts 16 and 17 of the transmission unit 15 to rotate around axis A.

[0189] The first and second planetary gear trains are configured such that the auxiliary shafts 16 and 17 rotate about axis A with corresponding angular velocities (N-1)*Ω and (N+1)*Ω in a reference system integral with the main shaft 50.

[0190] Specifically, the main shaft 50 and the first auxiliary shaft 16 rotate in the same direction, and the second auxiliary shaft 17 rotates in the opposite direction to the main shaft 50 and the auxiliary shaft 16.

[0191] The first auxiliary shaft 16 and the second auxiliary shaft 17 respectively drive the mass units 8 and 9, and in particular the corresponding mass bodies 10 and 11, to rotate around axis A with corresponding angular velocities (N-1)*Ω and (N+1)*Ω.

[0192] Additionally, during rotation about axis A, the masses 10 and 11 are pressed against the inner wall of the housing 12 by centrifugal force, thereby transferring the first and second damping results to the main shaft 50.

[0193] When the control unit 40 is deactivated, the actuator 58 is deactivated, and therefore the corresponding support assemblies 41 and 42 do not change the corresponding angle defined between them. In addition, the corresponding angular positions of the support assemblies 41 and 42 do not change relative to the fixed direction of rotation integrally with the associated auxiliary shafts 16 and 17.

[0194] As a result, in the above situation, although the support components 41 and 42 are installed in a manner that allows them to move angularly relative to the corresponding first auxiliary shaft 16 and second auxiliary shaft 17, they are driven by the corresponding auxiliary shafts 16 and 17 to rotate at corresponding angular velocities (N-1)*Ω and (N+1)*Ω.

[0195] Therefore, the rotation of support components 41 and 42 causes the associated mass bodies 10 and 11 to rotate eccentrically about axis A with corresponding angular velocities (N-1)*Ω and (N+1)*Ω.

[0196] The function of rotor 3 is described below with reference to the state of control unit 40, and in particular the state of actuator 58.

[0197] Reference Figure 6 The control unit 101 receives a signal from the sensor 100 that is associated with the acceleration state of the spindle 50, and generates a control signal for the actuator 58 of the control unit 40 when it detects that the phase and amplitude of the first damping resultant force and the second damping resultant force need to be changed.

[0198] Actuation of one or more actuators 58 causes the respective support assemblies 41 and 42 to rotate about axis A to position the masses 10 and 11 such that they define a desired respective angle between each other and are in a desired angular position relative to a fixed direction of rotation integral with the associated auxiliary axis 16 or 17.

[0199] More specifically and referring to mass unit 8 (9), the operation of an actuator 58 causes the corresponding output shaft 60 and gear 56 to rotate about the associated axis F.

[0200] The rotation of the associated gear 56 causes the associated support assembly 41 (42) to rotate an additional predetermined angle about axis A through the meshing of the corresponding control gear 57 and drive gear 55.

[0201] As a result, mass 10 (11) also rotates an additional predetermined angle about axis A relative to another mass 11 (10) and auxiliary axes 16 and 17.

[0202] The angle between the mass bodies 10 and 11 of mass unit 8 (9) is thus changed, and the magnitude of the first (second) attenuation resultant force is thus adjusted.

[0203] The positions of the mass bodies 10 and 11 of mass unit 8 (9) relative to the fixed direction are also changed, so the phase of the first (second) attenuated resultant force is changed relative to the fixed direction.

[0204] Special reference Figure 4 Reference numeral 7' indicates a damping device for rotor 3' according to a second embodiment of the present invention (shown only partially).

[0205] Attenuation device 7' is similar to attenuation device 7, and its differences from the latter will be described below only; where possible, the same or equivalent parts of attenuation devices 7 and 7' will be indicated by the same reference numerals.

[0206] Specifically, each attenuation device 7' differs from the other in that the drive gear teeth 55' of each control unit 40 are spaced apart from each other in both the radial and axial directions. In particular, a corresponding set of drive gear teeth 55' is arranged radially inward relative to axis A, and another set is arranged radially outward.

[0207] Furthermore, the inner diameter of one annular element 59' in each control unit 40 is larger than the outer diameter of the other annular element 59'. In particular, the corresponding annular element 59' with the larger inner diameter has drive gear teeth 55' arranged radially inward relative to the axis A, while the other annular element 59' has drive gear teeth 55' arranged externally.

[0208] Preferably, the annular element 59' with a larger inner diameter of each control unit 40 surrounds another annular element 59' of the control unit 40.

[0209] The difference between attenuation device 7' and attenuation device 7 is that arm 43 is directly connected to the corresponding annular element 59'.

[0210] Alternatively, each arm 43 can be mounted on a corresponding annular support, which is supported by a corresponding annular element 59'.

[0211] Specifically, the attenuation device 7' differs from the attenuation device 7 in that the support assemblies 41 and 42 each include a corresponding slider 65' adapted to couple the corresponding coupling element 47 to the corresponding arm 43 in a radially movable manner (see details). Figure 5Specifically, each slider 65' carries a corresponding coupling element 47 and is connected to the corresponding arm 43 in a radially movable manner.

[0212] The operation of the rotor 3' including the actuator 7' is similar to the operation of the rotor 3 with the actuator 7, so it will not be described in detail.

[0213] By examining the characteristics of the rotors 3 and 3' according to the invention, the advantages that can be achieved through them are obvious.

[0214] Specifically, rotor 3 or 3' is equipped with damping devices 7 or 7' that offer particular operational flexibility, effectively reducing vibrations originating from blade 5 and acting in a plane orthogonal to axis A. Specifically, damping devices 7 and 7' have a control unit 40 that can control the angle between the respective masses 10 and 11 in a particularly flexible and agile manner.

[0215] This is because the coupling between each set of gear teeth 57 and the corresponding set of gear teeth 55, 55' enables the mass bodies 10, 11 to rotate around axis A in two rotational directions.

[0216] In this way, unlike the known solutions described in the background section of this specification, the mass bodies 10 and 11 of the corresponding mass units 8 and 9 can be rotated in a direction that allows them to reach the desired position more quickly, thereby significantly improving the response characteristics of the attenuation devices 7 and 7'.

[0217] This is particularly advantageous when the direction of the vibration generated by the main shaft 50 in the rotor plane changes suddenly.

[0218] Furthermore, compared to the known solutions described in the background section of this specification, the coupling between each set of gear teeth 57 and the corresponding set of gear teeth 55, 55' can reduce the required transmission ratio.

[0219] As a result, the actuator 58 requires lower torque compared to the known solutions described in the background section of this specification.

[0220] This can limit the load on actuator 58 and further improve the response characteristics of damping devices 7, 7'.

[0221] Since each set of gear teeth 57 is reversibly coupled to a corresponding set of gear teeth 55, 55', the mass bodies 10, 11 of mass units 8, 9 will not remain blocked in the event of a failure of the associated actuator 58.

[0222] Therefore, the masses 10 and 11 of mass units 8 and 9 can be returned to their desired positions by corresponding springs (not shown).

[0223] Another advantage is that, since the mass bodies 10 and 11 of mass units 8 and 9 are axially inserted between the actuators 58 of mass units 8 and 9, the attenuation devices 7 and 7' have a small axial extension.

[0224] In other words, the extension of the attenuation devices 7 and 7' in the direction parallel to the rotation axis A of the main shaft 50 is substantially no more than the extension of the pneumatic conveyor 6 and therefore will not have an adverse effect on the aerodynamic properties.

[0225] In addition, since the first planetary gear train includes a portion shared with the second planetary gear train, the axial extension is also limited.

[0226] Another advantage is that the maintenance costs of the damping devices 7 and 7' are low due to the use of self-lubricating gear teeth.

[0227] Finally, the mass bodies 10 and 11 of each of the mass units 8 and 9 can move radially relative to axis A.

[0228] As a result, the centrifugal force generated by the rotation of the mass bodies 10 and 11 of each of the mass units 8 and 9 is released onto the shell 12.

[0229] This significantly reduces the bending loads acting on the auxiliary shafts 16 and 17 and other components of the transmission device 15.

[0230] Finally, it is obvious that modifications and variations can be made to the rotors 3, 3' described and illustrated herein without departing from the scope defined by the claims.

[0231] Specifically, the control unit 40 can cause only the support assemblies 41, 41' and only the mass 10 to undergo additional rotation about axis A relative to the associated auxiliary axes 16, 17. In this case, the support assemblies 42, 42' and the mass 11 will rotate integrally with the associated auxiliary axes 16, 17.

[0232] Masses 10 and 11 can have different values.

[0233] Rotor 3 can also be used in thrust-reversing aircraft instead of helicopter 1.

[0234] Finally, the rotor according to the invention can be the tail rotor of the helicopter 1 instead of the main rotor 3.

Claims

1. A rotor (3, 3') for a hovering aircraft (1), comprising: - Hub (4), which is rotatable about a first axis (A) and includes multiple blades (5); - A main shaft (50) that can be connected to the drive component of the aircraft (1) and operatively connected to the rotor hub (4) to drive the rotor hub (4) to rotate about the first axis (A) in use; - A damping device (7, 7') is configured to reduce the transmission of vibrations from the main shaft (50) in a plane orthogonal to the first axis (A); as well as - Transmission device (15), configured to transfer the rotation of the main shaft (50) about the first axis (A) to the attenuation device (7, 7') in use. The attenuation device (7; 7') includes at least a first mass unit (8, 9) and a second mass unit (9, 8), and each of the first mass unit (8, 9) and the second mass unit (9, 8) includes at least a first mass body (10, 11) and a second mass body (11, 10). The first mass body (10, 11) and the second mass body (11, 10) of the first mass unit (8, 9) and the second mass unit (9, 8) are rotatable about the first axis (A) and operatively connected to the main shaft (50) to generate a first centrifugal force and a second centrifugal force, respectively, having corresponding principal components in the radial direction relative to the first axis (A), on the main shaft (50). The transmission device (15) is configured to drive the first mass unit (8, 9) and the second mass unit (9, 8) to rotate relative to the main shaft (50) and around the first axis (A) in opposite directions at a first rotational speed ((N-1)*Ω; (N+1)*Ω) and a second rotational speed ((N+1)*Ω; (N-1)*Ω), respectively. The attenuation device (7, 7') further includes two control units (40), one of which is operatively connected to the first mass unit (8, 9) and the other is operatively connected to the second mass unit (9, 8). Each control unit is selectively operable to additionally rotate at least one of the first mass body and the second mass body (10, 11) of the associated first mass unit (8, 9) and the second mass unit (9, 8) relative to the transmission device (15), and selectively controls the relative angle between the first mass body (10, 11) and the second mass body (11, 10) of the associated first mass unit (8, 9) and the second mass unit (9, 8). The first mass unit (8, 9) and the second mass unit (9, 8) each include a corresponding first support component (41, 42) supporting the corresponding first mass body (10, 11) and a corresponding second support component (42, 41) supporting the corresponding second mass body (11, 10). Each of the control units (40) is operatively coupled at least to a corresponding first support assembly (41, 42) to rotate relative to the transmission device (15) about the first axis (A) and to control the relative angle between the first mass body (10, 11) and the second mass body (11, 10) of the corresponding first mass unit (8, 9) and second mass unit (9, 8). Each of the control units (40) includes at least: - A set of drive gear teeth (55, 55') which are integrally formed with the corresponding first support components (41, 42); - A gear (56) having a corresponding set of control teeth (57) meshing with the drive gear teeth (55, 55') and rotatable about a second axis (F) parallel to the corresponding first axis (A); and -Actuator (58) that can be operated to rotate the gear (56) about the second axis (F) and the corresponding first mass (10, 11) about the first axis (A) in use; The characteristic feature is that each of the actuators (58) is configured to selectively rotate the corresponding gear (56) about the first axis (A) in two rotational directions. Each set of control gear teeth (57) and a corresponding set of drive gear teeth (55, 55') enables the first mass body (10, 11) and the second mass body (11, 10) to rotate about the first axis (A) in two rotational directions. The first mass unit (8, 9) and the second mass unit (9, 8) each include a corresponding base support (45) rotatable about the first axis (A) and operatively connected to the transmission device (15) so as to be driven in use to rotate about the first axis (A) at the first rotational speed ((N-1)*Ω) and the second rotational speed ((N+1)*Ω), respectively. The corresponding first support assembly (41, 42) is rotatably connected to the corresponding base bracket (45) on the first side of the corresponding base bracket (45), and the corresponding actuator (58) is integrally connected to the base bracket (45) on the second side of the corresponding base bracket (45) that is axially opposite to the first side when traveling along the first axis (A).

2. The rotor according to claim 1, characterized in that, Each first actuator (58) includes an output shaft (60) coaxially connected to the corresponding gear (56).

3. The rotor according to claim 1, characterized in that, Each of the control units (40) includes an annular element (59) which is connected to the corresponding first support assembly (41, 42) and has a corresponding drive wheel tooth (55, 55') on its circumferential edge relative to the corresponding first axis (A).

4. The rotor according to claim 3, characterized in that, The drive wheel teeth (55) are located radially outside or inside relative to the corresponding first axis (A).

5. The rotor according to claim 1, characterized in that, The first mass body (8, 9) and the second mass body (10, 11) of the first mass unit (8, 9) and the second mass unit (9, 8) are axially inserted between the associated actuator (58).

6. The rotor according to claim 1, characterized in that, The first mass body (10, 11) and the second mass body (11, 10) of the first mass unit (8, 9) and the second mass unit (9, 8) are arranged radially outward relative to the associated actuator (58).

7. The rotor according to claim 1, characterized in that, The first support assembly (41, 42) and the second support assembly (42, 41) of the first mass unit (8, 9) and the second mass unit (9, 8) can both rotate about the first axis (A) relative to the transmission device (15). Each of the control units (40) is also operatively coupled to a corresponding second support assembly (42, 41) to rotate about the first axis (A).

8. The rotor according to claim 1, characterized in that, The drive gear teeth (55) of the first support assembly and the second support assembly (41, 42) overlap each other axially and are located at the same radial distance from the first axis (A).

9. The rotor according to claim 1, characterized in that, The drive gear teeth (55') of the first support assembly and the second support assembly (41, 42) are arranged at different radial distances from each other from the first axis (A) and face each other radially.

10. The rotor according to claim 1, characterized in that, Each of the first mass bodies (10, 11) and each of the second mass bodies (11, 10) is coupled to the corresponding first support assembly (41, 42) and second support assembly (42, 41) in a radially movable manner so as to be pressed against the radial inner wall of the housing (12) of the attenuation device (7, 7') in use.

11. The rotor according to claim 1, characterized in that, The transmission device (15) includes at least: - A first auxiliary shaft (16) is integrally formed with the first mass unit (8; 9) at an angle and is rotatable about the first axis (A); - A second auxiliary shaft (17), which is integrally formed at an angle with the second mass unit (9; 8) and is rotatable about the first axis (A); and - A conversion unit (18) is functionally coupled to the main shaft (50) and the first auxiliary shaft (16) and the second auxiliary shaft (17), and is configured to receive motion from the main shaft (50) and transfer the motion to the first auxiliary shaft (16) and the second auxiliary shaft (17), such that the first auxiliary shaft (16) and the second auxiliary shaft (17) rotate in use about the first axis (A) at a first rotational speed ((N-1)*Ω) in the same rotational direction as the main shaft (50) and about the first axis (A) at a second rotational speed ((N+1)*Ω) in the opposite direction of rotation of the main shaft (50).

12. The rotor according to claim 1, characterized in that, The first rotational speed is equal to (N-1)*Ω and the second rotational speed is equal to (N+1)*Ω, where N is the number of blades (5) and Ω is the rotational speed of the main shaft (50) in a reference frame integral with the fuselage (2). The first mass unit (8; 9) is rotatable in the same direction as the main shaft (50), and The second mass unit (9; 8) can rotate in the opposite direction to the main shaft (50).

13. The rotor according to claim 11, characterized in that, The transmission device (15) includes: - A first planetary gear train, functionally inserted between the main shaft (50) and the first auxiliary shaft (16); and - A second planetary gear train, which is functionally inserted between the main shaft (50) and the second auxiliary shaft (17), The first planetary gear system includes a portion shared with the second planetary gear system.

14. The rotor according to claim 1, characterized in that, The drive gear teeth (55, 55') and the control gear teeth (57) are made of self-lubricating materials and / or polymer materials.

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