KR20140049270A - Lead lag damper for a main rotor unit of rotary wing aircraft - Google Patents

Abstract

A lead lag damper (10, 11) for a helicopter rotor unit has a rotor and a hub (8). The rotor has an N number of rotor modes, wherein the N is the number of blades. The single lead lag damper (10, 11), which is the center part of the rotor unit, is essentially formed into the shape of a cylinder. Elastomeric substance shearing elements arranged between a first surface (7) and a second surface (9) has constant tolerance against shearing strain and are axially loaded in advance so that the lead lag damper (10, 11) can constantly act in rotor inplane eigenmodes. Thus, the lead lag damper (10, 11) acts as a single unit in the critical inplane modes of a rotor having an N number of identical blades (1-4). Elastomeric substances are loaded by the constant shearing strain in contrast with ordinarily used vibration strain.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a main lobe damper for a main rotor unit of a rotor blade aircraft,

The present invention relates to a lead lag damper for a main rotor unit of a rotorcraft aircraft such as a helicopter having a rotor and a hub.

The degree of freedom of each of the rotors may be described by N rotor modes, where N is the number of blades of the rotor. There are circulation modes (longitudinal and lateral), collective modes, and differential modes.

The critical regressive rotor inplane mode is a non-harmonic circulation mode. The main rotors of the rotorcraft aircraft feature a lead lag damping device that acts upon the planar motion of the rotor blades by converting shear deformation in the lead lag damping device into heat. The lead lag damping device comprises a retractable rotor planar mode configured by the lead-lag oscillation of the individual rotor blades as a result of the aerodynamic instability of the helicopter, i.e. the circular rotational displacement of the center of the rotating rotor blades relative to the hub of the helicopter, It is necessary to prevent air resonance and ground resonance caused by the interaction between the modes. The design and lay-out of the lead-lag damping device depends on the applied rotor concept.

Document US 5372478 describes a rotorcraft airplane rotor with flaps and lagged blades. A typical lag damper system is centered on the rotor's axis of rotation. The square shaped damper includes planar strips with rigid plates superimposed along the rotor axis with the elastomeric layers. Streams and layers are resiliently interconnected. Each rigid plate of this general lag system in the center is connected to only one separate blade root via a dedicated ball joint. Document US 5372478 corresponds to the specialized part of claim 1 of the main claim.

Document US 4297078 discloses a helicopter rotor having a rotor head arranged to support a plurality of rotor blades for rotation about an axis. The rotor head generally includes a hollow structure. Each rotor blade is supported by an elastomeric bearing arranged to allow blade flaps, lead / lag and feathering motion. The support means includes interconnected inner and outer elastomeric assemblies, of which the outer assembly is connected via a common elastomeric lead / lag damper unit providing inter-blade damping of blade lead / lag motion , And are connected to the respective rotor blades. The elastomeric assemblies are pre-compressed.

Document EP 0424267 describes drag-elastic-damping devices for rotor blades of rotor blades. Such a device includes a rotatable, member for elasto-return with integrated damping, the function of which is ensured by the circumferential shear of a viscoelastic material which is very stable to distortion, such as an elastomer. This ensures the elastic return of the blades to the neutral position in the drag. The connecting rod drives the outer armature and the lever of the corresponding member when rotating around the inner armature by a rotational joint. This inner armature is held in a fixed position relative to the hub. The flanges are secured to the inner armature on the peripheral zone of the hub between two adjacent blades.

Document WO2010068194 describes a rotor system with a lid stop plate mounted on a rotor hub arm and a lid stop mounted on a spindle, wherein such stop is operable to contact the lid stop plate. The rotor hub has a plurality of rigid hub arms.

Document US2007071602 discloses a flywheel rotor comprising at least two blades and a hub hinged by respective joints to the hub, for each pitch axis and for each flap axis, and for each lag axis. do. Each blade is secured to a respective pitch lever. The rotor includes respective pitch control rods connected to respective pitch levers by a first ball joint, and a general lag damper system substantially centered on the rotational axis of the rotor. Connected to each of the blades so that the damper system provides a respective second ball joint close enough to the first ball joint to connect the pitch rod to the pitch lever on the lag damper system such that the pitch load is relatively insensitive to flap oscillation of the hinged blades To the respective side projections from the respective blades. Viewed from above, the damper is a square frame, i.e. each "side" of the frame forms a respective damper unit, and these four identical damper units are paired together.

Conventional concepts of the prior art lead-lag damper cited prior art commonly have respective blades of a rotor with hinges and associated discrete elastomeric damping devices. The elastomeric material of the dampers undergoes linear shear deformation due to the rotational displacement of the applied circular. Planar motion of each blade of the rotor must be considered in the planar motion, which includes n / rev (n = 0, 1, 2, 3 ...- rev = revolution) and non-coherent displacement. The non-coherent displacements are derived from the planar eigenmodes of the blades of the rotor. The plane eigenmode overlaps the n / rev displacements. The combination of the circular non-coherent rotational displacement and the airframe mode may cause ground resonance if the damped interposition is not sufficient.

An object of the present invention is to provide a lead-lag damper for a main rotor unit having a simple structure with improved damping.

The solution is provided with a lead-lag damper for a main rotor unit having the features according to claim 1.

According to one embodiment of the present invention, there is provided a lead lag damper for a main rotor unit having a rotor and a hub in a rotor blade aircraft. The damper is adapted to be coaxially supported with the first of its faces on the hub. Said damper having at least one of linking means for linking said second face to said rotor at a second one of its faces or N identical blades (N = 3, 4, 5, 6 or more) of said rotor . The lead lag damper of the present invention has an essentially cylindrical shape. The second side of the damper faces the first side, and the elastomeric material present between the first side and the second side is resistant to shear deformation.

The present invention proposes a mechanical damper that directly acts in an associated rotor mode, i.e., a retraction rotor lag-lag mode, in which damping is essential. Therefore, the present invention improves the specific efficiency. A single center damper for the entire rotor ensures that each rotor blade "sees" the same stiffness of the damper. Therefore, the potential imbalance of the rotor is avoided. This imbalance can be caused by dispersion of individual damper properties (fabrication, aging ...).

Each of the linear vibrational shear motions of the prior art lead lag damper is required to be homogeneous and therefore in an optimal way to process the rotor plane eigenmodes as necessary for preventing ground resonance, Is replaced by a steady circular shear motion of the lead lug damper of the present invention which allows the loading of the polymeric material. The uniform loading of the lead lag damper of the present invention allows a lower specific shear stiffness of the elastomeric material and thus allows a more beneficial relationship between axial stiffness and shear stiffness so that the resulting ladder- There is an option for easier matching of the data.

The lead lag damper of the present invention works exclusively in the rotor plane (inplane) and is not pitch to one of the N blades. Therefore, no efficiency reduction is possible, and the lead-lag / pitch combination effect no longer depends on any blade pitch position. The lead lag damper of the present invention allows to reduce the influence of the shear stress amplitude on the damper stiffness, which reduces the risk of unintentional small limit cycle vibration of the helicopter. The steady circular shear motion of the lead lag damper of the present invention allows time-independent loss of mechanical action under steady operating conditions of the helicopter.

One single inventive lead lag damper per rotor unit is less weight, less bulky, and reduces the number of parts compared to a plurality of lead lag dampers per prior art rotor unit. According to the test results, the lead lag damper of the present invention provides a reduced specific stiffness, that is, the volume required per unit of stiffness is reduced, and as another advantage, the damping characteristics avoids non-linearity, Lt; RTI ID = 0.0 > elastomeric < / RTI > dampers of the prior art. The lead lag damper of the present invention allows a fully integrated deployment into the rotor unit with the potential for hub drag reduction. The space for the removal of the lead lag damper between the hub of the present invention and the rotor unit or the N blades is only needed in the circulation modes. The contribution of the aggregate modes does not require additional space. The design of the rotor unit may be more compact and the central principle of the lead lag damper of the present invention is applicable with most of the rotor hub concepts.

According to a preferred embodiment of the present invention, the lead lag damper has an essentially annular shape for improved adaptation to the hub of the rotor unit.

According to another embodiment of the present invention, the rotor includes a rotor star having a center space, and the lead lag damper is located in the center space of the rotor star for reduced drag.

According to another embodiment, the first face of the lead lag damper is clamped to the hub and the second face is linked to at least one control cuff of at least one blade.

According to one embodiment of the invention, the elastomer is bonded to the metal or fibrous parts of the first several and / or the second surface.

According to another embodiment, the lead lag damper is a spring / damping system.

According to one embodiment of the present invention, the lead lag damper is preloaded in the axial direction. To prevent tensions in the elastomeric material, preloading the damper in the axial direction does not need to be disturbed by the blade cuffs, thus saving space and volume. The pressure caused by the required preloading can be chosen to be lower because the peak loading applied to the elastomer is reduced.

According to another embodiment of the invention, two or more shear elements are applied to the hub, which simplifies, for example, axial pre-loading.

According to another embodiment of the invention, the shear elements are axially separated on the hub.

According to one embodiment of the invention, the interfaces with the hub, rotor and / or blades are interchangeable.

According to another embodiment of the present invention, stops are provided in the space at the center of the rotor. In the case of space constraints for free movement in the space at the center of the rotor of opposite faces of the lead lug damper to each other, contact with the stop is smooth and does not vibrate as in the case of the prior art linear damper. For example, by designing a suitable hard stop, nonlinear shear wire characteristics of the lead lag damper of the present invention can be generated.

According to one embodiment of the present invention, when the lead lag damper is located outside the open space at the center of the rotor, above or below the rotor plane, the linking means connects the blades of the rotor with the second face of the lead lag damper And rods and levers. This arrangement of the lead-lag damper outside the open space at the center is advantageous regardless of whether sufficient space is available at the center of the rotor.

According to another embodiment of the present invention, a shaft that is not coaxially rotated about the hub is provided, the first surface of the lead lag damper is clamped to the hub through the non-rotating shaft, To the at least one control cuff of the at least one blade. An advantage of this embodiment of the present invention is that the critical retraction rotor plane eigenmode has a frequency that is the difference between the rotor frequency and the natural plane blade frequency, resulting in circular motion of the non-rotating lead lag damper of the present invention. 1 / rev plane displacements deteriorate the steady displacement of the non-rotating lead lag damper of the present invention. Therefore, the number of fatigue load cycles of the elastomeric material is significantly reduced. The deviating static and dynamic shear stiffness properties of the elastomeric material can be used as design parameters for rotor lead-lag dynamics. The non-rotating lead lag damper of the present invention is designed so that when only the natural-circulating planar eigenmode is excited, the air frame modes at ground or after disturbance of steady flight conditions such as, for example, gusts, maneuvering, It is dynamically loaded only when coupled with resonance.

According to one embodiment, at least one shear element of the non-rotating lead lag damper of the present invention is clamped to the hub through the non-rotating shaft on its first face, Wherein at least one further shear element of the rotating lid lag damper of the present invention is clamped to the hub at its respective first face, Is coupled to at least one rotor blade on the second side of the rotor blade to combine the advantages of each of the non-rotating lead lag damper of the present invention with the advantages of each of the rotating lag damper of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention are illustrated in the following description with reference to the accompanying drawings.

1 is a schematic view of a lead lag damper according to the present invention;
Figure 2 is a schematic top view of a lead lag damper integrated into a rotor unit (N = 4) of four blades in accordance with the present invention.
3 is another schematic diagram of a lead lag damper according to the present invention;
4 is a schematic diagram of one embodiment of a double lead lag damper in accordance with the present invention;

1 and 2, the lead lag damper 10 is a spring / damping system that is clamped concentrically to the hub 8 of the main rotor unit on the first side 9. The second face 7 of the lead-lag damper 10 has N blades 1 to 4 (in this example, N = 1, 2, 3 and 4) of rotors in the essentially concentric state of a rotorcraft, such as helicopter A And links (17) such as rods and / or levers (Figure 2) which link each control cuff (6) with respect to each other. Each of the N blades 1 to 4 is provided with a lead lag hinge 5. The blade 3 precedes the rotation of the rotor unit representing the circulating planar eigenmode (C, Fig. 1) of the rotor, and the blade 1 is after rotation. The main rotor unit includes N blades 1 to 4 together with lead lugs 5 and control cuffs 6 and is referred to by reference numerals 1 to 6 in Figs.

1, in operation of the rotorcraft aircraft A, the first side 9 of the lead-lag damper 10 is moved relative to the second side 7 in the open space 18 inside the center of the rotor do.

1, the space restriction in the open space 18 at the center of the rotor unit is limited by the fact that the space in the axial direction G of the lead lag damper 10 (Fig. 1, Fig. 3, Is provided by the stop (12) to limit the movement between the first side (9) and the second side (7). The stops 12 are embodied as stiff stops or are implemented with stiffnesses having defined stiffness to allow design of non-linear damper stiffness characteristics with respect to the stalls 12 with defined stiffness. The stop portions 12 are mounted on the inner circumference of the open space 18 at the center of the rotor.

1, the second face 7 of the lead lag damper 10 has a rotor star 13, such as a planar flex beam unit, as an interface between the hub 8 and the plurality of rotor blades 1 to 4, . The rotor star 13 forms a planar flex beam unit made of a composite compound having an odd number of essentially planar torque arms. Each torque arm is present on either side along its radial extension and has an essentially concave profile integral with its adjacent torque arms in the root area of the torque arm of relatively large width I have. The rotor star 13 is provided with an essentially circular opening which forms, for example, the open space 18 at its center for containing the lead lag damper 10.

The lead lug damper 10 is preloaded to the hub 8 in the coaxial direction. The lead lag damper 10 has an annular shape and is filled with an elastomer between the first side 9 and the second side 7. The first side 9 and the second side 7 are made of metal parts and / or fibrous parts. The elastomer is bonded to the first side (9) and the second side (7) to form elastomeric shear elements (14).

The circular reed-lag movement of the rotating blades 1 to 4 causes the lead lag damper 10 to move in a circulating manner (i.e., the circulating plan eigenmodes C) (F, Figs. 1 to 4) that cause circular shear deformation at the front end elements 14 between the face 9 and the second face 7. [

Fig. 1 shows, as a sample, time variant forces F resulting from the circulating lead-lag motion of one of the blades 1 to 4. The resulting circular motion (circular planar eigenmode C) around the hub 8 causes a corresponding circular shear deformation of the lead lag damper 10.

Fig. 2 shows, as a sample, how the lead lag damper 10 is moved due to the forces of the circulating planar rotor eigenmode and the N blades 1 to 4. The sum of the forces F of all the N blades 1 to 4 at the positions shown leads to one displacement of the lead lag damper 10 versus azimuth angle. The displacement represents a moment of circular motion of the lead lag damper 10 due to the rotation of the blades 1 to 4 in the steady state of flight of the rotorcraft A. [

The effective stiffness of the elastomeric front end elements 14 of the lead lag damper 10 is adjusted according to the rotor modes that can be used as design parameters. Circular mode stiffness is due to circular motion.

Referring to FIG. 3, the same reference is used for the corresponding features in FIG. 1 and FIG. 3 shows, as a sample, the time-varying forces of the collective planar mode of a blade cuff of one of the blades 1 to 4 and the hub 8, which causes oscillating circular shear deformation of the lead lag damper 10, Lt; RTI ID = 0.0 > torsional < / RTI > The collective modes are the temporally synchronized motions of all the blades of the rotor without opposing the aerodynamic stability of the rotor aircraft (A). The collective stiffness is due to the torque motion, and since the elastomeric material is a bridge, the differential stiffness is significantly higher.

According to Fig. 4, the same reference is used for the corresponding features in Figs. Two preloaded elastomeric shear elements 14 are coaxially applied to the hub 8 along the axial direction G to form one double lid lag damper 10. The two lid lag damper 10 are shown in Fig. Each of the shear elements 14 corresponds to one lead-lag damper 10, as in Figures 1-3, in which case the respective second faces 9 of each elastomeric shear element 14 Contact each other.

The interfaces 19 of the lead-lag damper 10 are shown in FIG. This interface 19 links the lead lag damper 10 to the hub 8 and the blades 1 to 4. These interfaces 19, such as rods and / or levers, may be exchanged between the first side 9 and the second side 7.

1 and 3 to 4, a central space 11 coaxial with respect to the axial direction G is provided inside the lead lag damper 10.

In Fig. 3, the lead lag damper 10 is clamped to the non-rotating shaft 15 of the rotor unit. The non-rotating shaft 15 is coaxially positioned around the rotating shaft of the hub 8. [ The lead lag damper 10 is clamped on its first face 7 to such a non-rotating shaft 15 and the second face 9 is clamped through the bearing ring 16 to the at least one blade 1, 4) of at least one control cuff (6). The bearing ring 16 is the linking means 17 and is coaxially positioned around the non-rotating shaft 115. This total lead lag damper 10 with the non-rotating shaft 15 does not rotate.

One embodiment suggests a lead lag damper 10,11 wherein the second side 7 of this damper is linked to each of the N blades of the rotor unit (e.g., 1 to 4) 9) are fixed in a minimum translational motion in the rotor plane.

In another example, the lead lag damper 10, 11 is fixed in a translational manner and rotatably in a fixed rotor plane with a second surface 7 linked to each of the N blades (e.g., 1 to 4) And has a first side (9).

In another example, the lead lag damper 10, 11 includes a first face 9 linked to each of the N blades (e.g., 1 to 4) and a second face 9 fixed in a minimal translational motion in the rotor plane (7).

One example is that the first face 9 is linked to each of the N blades (e.g., 1 to 4) and the second face 7 is coupled to the lead lag damper 10 , 11).

Claims (17)

In a lead lag damper (10) relating to a rotor unit (1 to 6) of a rotorcraft,
The rotor unit has a rotor and a hub (8), the damper (10) has a first face (9) and a second face (7), coaxial with the first face (9) on the hub (8). And a linking means 17 adapted to be supported in the direction and linking the second face 7 to the rotor or at least one blade 1 to 4 of the rotor at the second face 7. ,
The damper 10 is a single lead lag damper 10 in the center for the entire rotor unit and has an essentially cylindrical shape, with the second face 7 being the first in the axial direction of the hub 8. The elastomeric material disposed facing the face 9 and between the first face 9 and the second face 7 is a shear element 14 that is resistant to shear deformation, and the lead lag damper 10 ) Is a spring / damping system preloaded in the axial direction such that the lead lag damper (10, 11) acts in a homogeneous manner in the rotor in-plane eigenmode.
The method according to claim 1,
The lead lag damper (10) has an essentially annular shape, and a center space (11) is located at the center of the lead lag damper (10).
The method according to claim 1,
Wherein the rotor unit comprises an open space (18) in the center of the rotor unit and the damper (10) is centered in the open space (18) of the rotor units (1 - 6).
The method according to claim 1,
The first face 9 of the lead lag damper 10 is clamped to the hub 8 and the second face 7 is secured to at least one control cuff of at least one blade 1, (6).
The method according to claim 1,
The elastomeric shear element (14) is bonded to the metal parts and / or the fiber parts of the first face (9) and / or the second face (7).
The method of claim 3, wherein
Wherein the rotor unit comprises a rotor star with an open space and the lead lag damper is located in the center space of the rotor star, Lag damper.
The method according to claim 1,
Wherein two or more elastomeric shear elements (14) are provided, the elastomeric shear element (14) being supported by the hub (8).
The method of claim 7, wherein
Wherein the elastomeric shear element (14) is axially separated on the hub (8).
The method according to claim 1,
The lead lag damper, wherein the hub (8), the rotor and / or the blades (1 to 4) are linked to the lead lag damper (10) by exchangeable interfaces (19).
The method of claim 3, wherein
Stops 12 are provided in the open space 18 at the center of the rotor unit, the stops 12 having hard stops and / or defined stiffness. Lead lag damper with stops.
The method of claim 3, wherein
The linking means 17 is located at the center of the rotor units 1 to 6 and at the outside of the open space 18 above or below the rotor plane of the blades 1 to 4. The lead lag damper 10. The lid lug damper as claimed in claim 1, wherein the second side (7) of the lead lag damper (10) has rods and levers connecting the second side (7).
5. The method of claim 4,
A shaft (15) is provided around the hub (8) that is not coaxially rotated and the first surface (9) is clamped to the hub (8) through the non-rotating shaft (15) The two sides 7 are connected to the at least one control cuff 6 of the at least one blade 1 through 4 via a linking means 17 comprising a rotating bearing 16, .
13. The method according to claim 7 or 12,
At least one elastomeric shear element is clamped to the hub 8 via the non-rotating shaft 15 at the first face 9 and at the second face 7 of the linking means 17. The at least one control cuff 6 of the at least one blade 1-4 is clamped through a rotating bearing 16, at least one of the other elastomeric shear elements 14 having a respective first face. Lead lag damper, characterized in that it is clamped to the hub (8) at (9) and to the at least one blade (1 to 4) at each second face (7).
The method according to claim 1,
The second face 7 of the lead lag dampers 10, 11 is linked to each of the N blades 1 to 4 of the rotor unit, the first face 9 having a minimum translational motion in the rotor plane. Reed lag damper, characterized in that fixed in the manner.
The method according to claim 1,
The second face 7 of the lead lag damper 10, 11 is linked to each of the N blades (e.g., 1 to 4) of the rotor unit and the first face 9 is translated in a rotor plane And is fixed to be rotatable.
The method according to claim 1,
The first face 9 of the lead lag dampers 10, 11 is linked to each of the N blades (eg 1 to 4) of the rotor unit, and the second face 7 has a minimum translational motion in the rotor plane. Reed lag damper, characterized in that fixed in the manner.
The method according to claim 1,
The first face 9 of the lead lag damper 10, 11 is linked to each of the N blades of the rotor unit (e.g. 1 to 4) and the second face 7 is linked in a translational manner And is fixed to be rotatable.

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