ROTOR BLADE ASSEMBLY AND ROTORIC-WING AIRCRAFT

Abstract

To improve performance and / or operability of folding rotor blades of a rotorcraft equipped with a lead-lag damper. In a rotor blade assembly, the rotor head has a rotor rotational axis and a lead lag hinge axis. The rotor blade is connected to the rotor head so as to rotate about the lead lag hinge axis relative to the rotor head and has a base defining a first through hole. The lead lag damper has a damper body located closer to the rotor rotational axis than the base of the rotor blade when viewed in the direction of the rotor rotational axis, a blade connection portion defining a second through hole and connected to the rotor blade, and a rotor head connection portion. The lead lag fastener is inserted into the first through hole and the second through hole and connects the rotor blade to the blade connection portion of the lead lag damper.

Description

[Technical Field]

[0001] The present invention relates to a rotor blade assembly for a rotorcraft. [Background technology]

[0002] In the field of helicopters, there is a demand for a compact helicopter in which the rotor blades can be rotated and folded relative to the rotor head and aligned at the rear of the helicopter body in order to facilitate storage and transportation of the helicopter.

[0003] Furthermore, helicopters equipped with lead-lag hinges to release the Coriolis force generated by flapping have been known. These types of helicopters are often equipped with a lead-lag damper, as disclosed in Patent Document 1 below, to attenuate the rotational displacement of the rotor blades caused by the lead-lag hinges and prevent ground resonance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 4,028,000 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional helicopters equipped with lead lag dampers leave room for improvement in terms of rotor blade folding. For example, in the helicopter described in Patent Document 1, the lead lag damper is located at the base of the rotor blade and directly beside the tip of the rotor hub. Therefore, even if the lead lag damper is disassembled to the extent that the rotor blade can rotate, the rotor blade can only be rotated in the opposite direction from the lead lag damper, limiting the degree of freedom in folding the rotor blade. Furthermore, disassembling the lead lag damper is complicated, and reassembling the lead lag damper before using the helicopter is also complicated. This places a heavy burden on workers. The above problems are not limited to helicopters, but are common to various rotorcraft equipped with lead lag dampers. For these reasons, improvements in performance and / or ease of folding the rotor blades are desired. [Means for solving the problem]

[0006] This specification discloses a rotor blade assembly. The rotor blade assembly includes a rotor head, a rotor blade, a lead lag damper, and a lead lag fastener. The rotor head has a rotor rotation axis and a lead lag hinge axis. The rotor blade is connected to the rotor head to rotate about the lead lag hinge axis relative to the rotor head and has a base defining a first through hole. The lead lag damper has a damper body located closer to the rotor rotation axis than the base of the rotor blade when viewed in the direction of the rotor rotation axis, a blade connection portion defining a second through hole and connected to the rotor blade, and a first rotor head connection portion connected to the rotor head. The lead lag fastener is inserted into the first through hole and the second through hole and connects the rotor blade to the blade connection portion of the lead lag damper.

[0007] According to this rotor blade assembly, once the lead lag fastener is removed from the first through hole and the second through hole, the rotor blade can be rotated about the lead lag hinge axis to fold the rotor blade without disassembling the lead lag damper. This simplifies the rotor blade folding process, improving user operability. Furthermore, this rotor blade assembly does not require a dedicated mechanism for folding the rotor blade, simplifying the device configuration. Furthermore, the damper body of the lead lag damper is located closer to the rotor rotation axis than the base of the rotor blade when viewed in the rotor rotation axis direction. Therefore, when folding the rotor blade, the user can rotate the rotor blade toward the damper body in addition to away from the damper body. This improves the degree of freedom in folding the rotor blade. In other words, the rotor blade folding performance of the rotor blade assembly is improved.

[0008] This specification further discloses a rotor blade assembly including a rotor head, a rotor blade, a lead lag damper, and a lead lag fastener. The rotor head has a rotor rotation axis and a lead lag hinge axis. The rotor blade has a base coupled to the rotor head for rotation about the lead lag hinge axis relative to the rotor head and defining a first through hole. The lead lag damper has a damper body, a blade connection portion defining a second through hole and coupled to the rotor blade, and a rotor head connection portion coupled to the rotor head. The lead lag fastener is inserted into the first through hole and the second through hole and connects the rotor blade to the blade connection portion of the lead lag damper. With the lead lag fastener removed from the first through hole and the second through hole, the rotor blade rotates a predetermined angle around the lead lag hinge axis toward the side opposite the lead lag damper, and the rotor blade rotates a predetermined angle around the lead lag hinge axis toward the lead lag damper without interfering with the lead lag damper.

[0009] With this rotor blade assembly, once the lead lug fastener is removed from the first through hole and the second through hole, the rotor blade can be rotated about the lead lug hinge axis to fold the rotor blade without disassembling the lead lug damper. Furthermore, during the rotor blade folding operation, the user can rotate the rotor blade not only away from the damper body but also toward the damper body. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a helicopter with rotor blades in use according to one embodiment; [Figure 2] FIG. 2 is a partially enlarged view of FIG. [Figure 3] 1 is a perspective view of a helicopter with rotor blades in a folded position. [Figure 4] 1 is a perspective view of a helicopter with rotor blades in a folded position. [Figure 5] FIG. 2 is a partial perspective view of a rotor head. [Figure 6] FIG. 2 is a partial plan view showing a connecting portion between the rotor head and the rotor blades. [Figure 7] FIG. 2 is a partial plan view of the connection portion between the rotor head and the rotor blade, with one of the pair of arms, more specifically the upper side of the fuselage, removed. [Figure 8] FIG. 2 is a partial side view showing a connecting portion between the rotor head and the rotor blades. [Figure 9] FIG. 9 is a cross-sectional view taken along the line AA in FIG. 8. [Figure 10] FIG. 10 is a partially enlarged view of FIG. [Figure 11] FIG. 7 is a cross-sectional view taken along the line BB in FIG. 6. [Figure 12] FIG. 10 is a perspective view showing a state in which the lead lag fastener has been removed and the rotor blade has been rotated to the side opposite the lead lag damper. [Figure 13] FIG. 10 is a perspective view showing a state in which the lead lag fastener has been removed and the rotor blade has been rotated in a direction toward the lead lag damper. DETAILED DESCRIPTION OF THE INVENTION

[0011] A helicopter 10 according to one non-limiting embodiment of a rotorcraft will be described below with reference to the drawings. In this embodiment, the helicopter 10 is an unmanned aircraft. The helicopter 10 may also be a manned aircraft. As shown in FIG. 1 , the helicopter 10 includes a fuselage 11 and a rotor blade assembly 15. The rotor blade assembly 15 includes a rotor head 20, also referred to as a rotor hub, and three rotor blades 30. The number of rotor blades 30 may be four or more.

[0012] As shown in FIGS. 2 and 5 , the rotor head 20 is attached to the rotor shaft 12 extending from the top of the airframe 11 and rotates together with the rotor shaft 12 about a rotor rotational axis AX1. In this specification, the term "axis" refers to an imaginary line representing the center of rotation. As shown in FIG. 5 , the rotor head 20 includes a head main body 21. The head main body 21 includes a base 22 and three extensions 23. The base 22 is an annular portion attached to the rotor shaft 12. The rotor rotational axis AX1 extends through the center of a through hole in the base 22. The three extensions 23 extend from the base 22 radially outward from the rotor rotational axis AX1. The rotor head 20 further includes a first connecting member 24 and a second connecting member 25 corresponding to the three extensions 23, respectively.

[0013] As shown in FIGS. 5 and 6 , second connecting members 25 are connected to the three extension portions 23. FIGS. 5 and 6 show details of one set of extension portions 23 and second connecting members 25. The first connecting member 24 is disposed at the end of the second connecting member 25, extending with its longitudinal direction being the radial direction of the rotor rotational axis AX1. The first connecting member 24 and the second connecting member 25 are connected by fasteners 27. In this embodiment, the fasteners 27 include bolts and nuts. The first connecting member 24 includes a base 24 a, an upper blade connecting member 24 b, and a lower blade connecting member 24 c. The base 24 a is connected to the second connecting member 25. As shown in FIG. 8 , the upper blade connecting member 24 b and the lower blade connecting member 24 c branch out vertically from the base 24 a and extend radially outward.

[0014] In this embodiment, the first connecting member 24 and the second connecting member 25 are made of different materials. In this embodiment, the first connecting member 24 is made of an aluminum alloy, and the second connecting member 25 is made of steel. The materials of the first connecting member 24 and the second connecting member 25 are not particularly limited, and any material can be selected.

[0015] 2 and 5, the extension portions 23, the first connecting members 24, and the second connecting members 25 are arranged at equal intervals in the circumferential direction around the rotor rotation axis AX1. The rotor blade assembly 15 includes three extension portions 23, three first connecting members 24, and three second connecting members 25, all of which have the same configuration.

[0016] As shown in FIGS. 5 and 8 , the base 31 of the rotor blade 30 is inserted between the upper blade connecting member 24b and the lower blade connecting member 24c. In this state, the upper blade connecting member 24b, the base 31, and the lower blade connecting member 24c are connected by a fastener 26 that passes through them. In this embodiment, the fastener 26 includes a bolt and a nut. With this configuration, the rotor blade 30 is connected to the first connecting member 24 so as to rotate relative to the first connecting member 24 about the lead-lag hinge axis AX2. The lead-lag hinge axis AX2 coincides with the center line of the fastener 26 along the longitudinal direction and also coincides with the centers of the through holes through which the fastener 26 passes in the upper blade connecting member 24b and the lower blade connecting member 24c.

[0017] The second connecting member 25 is connected to the extension portion 23 via a feathering hinge, and rotates relative to the extension portion 23 about a pitch axis AX3 that is perpendicular to the lead-lag hinge axis AX2.

[0018] As shown in FIGS. 2 and 5 , the rotor blade assembly 15 further includes three lead lag dampers 40. Only two lead lag dampers 40 are shown in FIG. 5 . Each of the lead lag dampers 40 is disposed on one side of the extension portion 23, the first connecting member 24, and the second connecting member 25 in the rotation direction of the rotor head 20. In this embodiment, each of the lead lag dampers 40 is disposed on the leading edge side of the extension portion 23, the first connecting member 24, and the second connecting member 25 in the blade rotation direction of the rotor head 20. The leading edge side in the blade rotation direction of the rotor head 20 is the direction in which the rotor blades 30 move when the rotor head 20 rotates, and is opposite to the trailing edge side in the blade rotation direction of the rotor head 20.

[0019] The lead-lag damper 40 is connected to the rotor blade 30 and at least one of the first connecting member 24 and the second connecting member 25 of the rotor head 20, and damps the lead-lag motion of the rotor blade 30 to prevent ground resonance and the like when the helicopter 10 is in use. The lead-lag motion is a rotational displacement of the rotor blade 30 about the lead-lag hinge axis AX2. Specifically, the lead-lag damper 40 includes a first damper body 41 and a second damper body 42, a blade connecting portion 43, a first rotor head connecting portion 48 and a second rotor head connecting portion 49, a first base 50 and a second base 51, as shown in FIG. 7 .

[0020] The first damper body 41 and the second damper body 42 include elastic bodies. As shown in FIGS. 7 and 9, the first damper body 41 and the second damper body 42 are arranged side by side in a direction intersecting the direction AX3d in which the pitch axis AX3 extends. Also, as shown in FIG. 5, the first damper body 41 and the second damper body 42 are located closer to the rotor rotational axis AX1 than the base 31 of the rotor blade 30 when viewed in the rotor rotational axis direction AX1d. The rotor rotational axis direction AX1d is the direction in which the rotor rotational axis AX1 extends. As shown in FIGS. 7 and 9, the first rotor head connecting portion 48 has a substantially L-shaped configuration. The generally L-shaped first rotor head connecting portion 48 is formed by connecting a first portion 48a extending in a direction along the pitch axis AX3 and a second portion 48b extending in a direction generally perpendicular to the pitch axis AX3 when viewed in the lead-lag hinge axial direction AX2d. The lead-lag hinge axial direction AX2d is the direction in which the lead-lag hinge axis AX2 extends. The first damper body 41 and the second damper body 42 are arranged to sandwich the first portion 48a therebetween.

[0021] 7 and 9, the first base 50 and the second base 51 have a generally disk-like shape. The first base 50 and the second base 51 are spaced apart from each other so as to sandwich the first damper body 41, the first portion 48a, and the second damper body 42 in the direction in which the first damper body 41, the first portion 48a, and the second damper body 42 overlap. Hereinafter, the direction in which the first damper body 41, the first portion 48a, and the second damper body 42 overlap will also be referred to as the stacking direction.

[0022] 7 and 9, the first base 50 and the second base 51 are pressed toward each other, in other words, in the stacking direction, by a pressing member 52. This compresses the first damper body 41 and the second damper body 42, generating an appropriate shear load during lead-lag movement and damping the lead-lag movement. In this embodiment, the pressing member 52 includes a bolt and a nut.

[0023] As shown in FIG. 10 , the first portion 48a of this embodiment has an opening 148a penetrating in the stacking direction. The first base 50 also has a protrusion 50a that protrudes toward the first portion 48a in the stacking direction and an opening 50b penetrating the inside of the protrusion 50a. More specifically, the protrusion 50a is part of a bushing that is press-fitted into the first base 50 and protrudes. The first damper body 41 also has a protrusion 41a that protrudes toward the first portion 48a in the stacking direction and an opening 41b that penetrates in the stacking direction and passes through the protrusion 41a. The protrusion 41a fits into the through opening 148a of the first portion 48a. The protrusion 50a of the first base 50 also fits into the through opening 41b of the first damper body 41.

[0024] As shown in FIG. 10 , the second base 51 has a protrusion 51a that protrudes toward the first portion 48a in the stacking direction and an opening 51b that penetrates the inside of the protrusion 51a. More specifically, the protrusion 51a is part of a bushing that is press-fitted into the second base 51 and protrudes. The second damper body 42 has a protrusion 42a that protrudes toward the first portion 48a in the stacking direction and an opening 42b that penetrates in the stacking direction and passes through the protrusion 42a. The protrusion 42a fits into the through opening 148a of the first portion 48a. That is, the protrusion 41a of the first damper body 41 and the protrusion 42a of the second damper body 42 fit into each other through the openings of the through opening 148a of the first portion 48a and face each other in the stacking direction. Furthermore, the protrusion 51a of the second base 51 fits into the through opening 42b of the second damper body 42. The bolts of the pressing member 52 are inserted through the respective through openings 50b, 41b, 148a, 42b, and 51b and tightened, thereby pressing the first base 50 and the second base 51 in the stacking direction.

[0025] As shown in FIGS. 5 and 8 , the blade connecting portion 43 includes a pair of arms 44, 45. The pair of arms 44, 45 are plate-shaped members and are spaced apart in the lead-lag hinge axial direction AX2d by a distance greater than the thickness of the base portion 31 when the rotor blade 30 is rotated between the arms 44, 45 about the lead-lag hinge axis AX2, i.e., the width in the lead-lag hinge axial direction AX2d. The pair of arms 44, 45 are plate-shaped members and extend parallel to each other. The longitudinal side of each of the arms 44, 45 closer to the rotor rotational axis AX1 has a substantially pentagonal shape. The longitudinal side of each of the arms 44, 45 farther from the rotor rotational axis AX1 extends longer and thinner than the substantially pentagonal shape when viewed in the rotor rotational axis AX1 direction. Hereinafter, the longitudinal portions of the arms 44, 45 closer to the rotor rotational axis AX1 will be referred to as inner portions, and the longitudinal portions farther from the rotor rotational axis AX1 will be referred to as outer portions. The inner portions of the arms 44, 45 are connected to the first base 50 and the second base 51 by fasteners so as to sandwich the first base 50 and the second base 51 in a direction perpendicular to the stacking direction. In this embodiment, the inner portions of the arms 44, 45 sandwich the first base 50 and the second base 51 from the direction AX1d in which the rotor rotational axis AX1 extends. In this embodiment, the fasteners include bolts and nuts.

[0026] Outer portions of the arms 44, 45 are connected to the base 31 of the rotor blade 30. Specifically, as shown in FIGS. 5 and 6 , the base 31 includes a lead lag damper connecting portion 33 on the side where the lead lag damper 40 is located in the circumferential direction around the lead lag hinge axis AX2. The lead lag damper connecting portion 33 is a portion that protrudes in a direction substantially perpendicular to the longitudinal direction of the rotor blade 30. In this embodiment, the protruding direction of the lead lag damper connecting portion 33 is perpendicular to the direction AX2d in which the lead lag hinge axis AX2 extends. The lead lag damper connecting portion 33 has a thickness smaller than that of the other portions of the base 31. As shown in FIG. 9 , the lead lag damper connecting portion 33 defines a first through hole 32 that penetrates the base 31 in its thickness direction. In this embodiment, the thickness direction is the direction of the lead lag hinge axis AX2.

[0027] As shown in FIG. 11 , outer portions of the arms 44, 45 define second through holes 46, 47 near their front ends. The second through holes 46, 47 penetrate the arms 44, 45, respectively, in the thickness direction. The arms 44, 45 are connected to the lead lag damper connection portion 33 of the rotor blade 30 using the first through hole 32, the second through holes 46, 47, and the lead lag fastener 60. In other words, the lead lag fastener 60 is inserted consistently through the first through hole 32 and the second through holes 46, 47 of the lead lag damper connection portion 33, thereby connecting the arms 44, 45 to the lead lag damper connection portion 33. As shown in FIG. 5 , in this embodiment, the lead lag fastener 60 includes a bolt 61, a bushing 64, and a retaining pin 66. The bolt 61 has a knob on its head.

[0028] As shown in FIG. 11 , the bolt 61 includes a head and a shank. The bolt 61 includes a tip 63 on the shank opposite the head. The tip 63 has a smaller diameter than the remaining portion. In other words, the shank of the bolt 61 includes a stepped portion on the opposite side of the head. The outer peripheral surface of the tip 63 includes a male thread. The bushing 64 is partially disposed within the second through-hole 47 of the arm 45. Specifically, the bushing 64 includes a stepped portion on its outer diameter. The bushing 64 is inserted into the second through-hole 47 of the arm 45 until the stepped portion of the bushing 64 abuts against the arm 45. In this embodiment, the bushing 64 is firmly fixed to the arm 45 by press-fitting in the direction AX2d along which the lead-lag hinge axis AX2 extends, from the arm 45 toward the lead-lag damper coupling portion 33. However, the bushing 64 may be fitted into the inner surface of the arm 45 without being press-fitted. The bushing 64 has two inner surfaces. One of the inner surfaces is located farther from the lead-lag damper connection portion 33 and has a relatively small inner diameter, while the other is located closer to the lead-lag damper connection portion 33 and has a relatively large inner diameter. A step is formed between the two inner surfaces. The inner surface with the relatively small diameter of the bushing 64 has a female thread portion 65 that screws onto the male thread of the tip portion 63. A bushing is also disposed in the second through hole 46 of the arm 44. This bushing does not have a female thread.

[0029] As shown in FIG. 11 , the bolt 61 is inserted into the first through hole 32 of the lead-lag damper connecting portion 33 of the rotor blade 30 and the second through holes 46 and 47 of the arms 44 and 45 until the male thread of the tip portion 63 is threadedly engaged with the female thread portion 65 of the bushing 64. The fully inserted position of the bolt 61 is determined by the abutment between a stepped portion adjacent to the female thread portion 65 of the bolt 61 and a stepped portion on the inner surface of the bushing 64, and by the abutment between the head of the first damper body 41 and the bushing inserted in the second through hole 46 of the arm 44. In this state, a retaining pin 66 is inserted into the through hole of the tip portion 63, thereby preventing the bolt 61 from loosening. With this configuration, the arms 44 and 45 are connected to the lead-lag damper connecting portion 33 of the rotor blade 30. The use of a bushing 64 with internal threads 65 rather than a nut reduces the number of parts and eliminates the risk of losing the nut. In alternative embodiments, the lead lug fastener 60 may be any form of fastener other than that described above.

[0030] According to the above-described configuration, portions of the arms 44, 45 are located at positions farther from the rotor rotational axis AX1 as viewed in the rotor rotational axis direction AX1d than the first damper body 41 and the second damper body 42. Furthermore, the arms 44, 45 extend from the base 31 of the rotor blade 30 to the first damper body 41 and the second damper body 42. This allows the first damper body 41 and the second damper body 42 to be connected to the rotor blade 30 via an efficient path.

[0031] The first rotor head coupling portion 48 and the second rotor head coupling portion 49 are coupled to the rotor head 20. Specifically, as shown in FIG. 7 , the tip of the second portion 48b of the first rotor head coupling portion 48 is coupled to the second coupling member 25 of the rotor head 20. In this embodiment, the first coupling member 24, the second coupling member 25, and the second portion 48b are fastened together by a fastener 29. This couples the first coupling member 24 and the second coupling member 25, and also couples the rotor head 20 and the first rotor head coupling portion 48. This configuration simplifies the device configuration and reduces the number of parts compared to when the first coupling member 24 and the second coupling member 25 and the rotor head 20 and the first rotor head coupling portion 48 are coupled separately. In this embodiment, the fastener 29 is in the form of a bolt and nut. However, fastener 29 may also be in the form of a fastener that provides irreversible fastening, such as a rivet.

[0032] As shown in FIG. 7 , the second rotor head connection portion 49 is located closer to the rotor blades 30 in the pitch axis direction AX3d than the first rotor head connection portion 48. The second rotor head connection portion 49 is spaced apart from the first rotor head connection portion 48 in the pitch axis direction AX3d and extends from a base of the second portion 48b to the first connection member 24. The pitch axis direction AX3d is the direction in which the pitch axis AX3 extends. The second rotor head connection portion 49 is connected at its tip to the first connection member 24 by the fastener 28. As shown in FIG. 8 , the second rotor head connection portion 49 has a hollow portion and includes two portions extending apart in the lead-lag hinge axis direction AX2d. This allows the second rotor head connection portion 49 to be lightweight while maintaining sufficient strength.

[0033] According to the rotor blade assembly 15 described above, the rotor blade 30 is rotatable about the lead-lag hinge axis AX2 relative to the rotor head 20. The lead-lag damper 40 is connected to the rotor blade 30 and the first connecting member 24 of the rotor head 20. Therefore, the rotor blade 30 is restricted from freely rotating about the lead-lag hinge axis AX2, but is able to perform lead-lag motion about the lead-lag hinge axis AX2.

[0034] When lead-lag motion occurs, a displacement load is transmitted to the first base 50 and the second base 51 via the first rotor head connecting portion 48. As a result, the first damper body 41 and the second damper body 42 undergo shear deformation relative to the first base 50 and the second base 51, thereby damping the lead-lag motion. The displacement limits of the lead-lag motion are restricted by the displacement limits of the first damper body 41 and the second damper body 42.

[0035] Furthermore, the rotor blade assembly 15 improves the performance and operability of folding the rotor blades 30. Specifically, by simply removing the lead lug fastener 60 from the first through-hole 32 of the rotor blade 30 and the second through-hole 46 of the blade connecting portion 43, the user can rotate the rotor blade 30 about the lead lug hinge axis AX2, thereby folding the rotor blade 30, without disassembling the lead lug damper 40. This simplifies the folding of the rotor blades 30, improving the user's operability. Moreover, since no dedicated mechanism for folding the rotor blades 30 is required, the device configuration can be simplified.

[0036] Furthermore, the first damper body 41 and the second damper body 42 are located closer to the rotor rotational axis AX1 than the base 31 of the rotor blade 30 when viewed in the rotor rotational axis direction AX1d. Therefore, when folding the rotor blade 30, the user can rotate the rotor blade 30 by a predetermined angle in either a direction away from the corresponding lead lag damper 40 or a direction toward the corresponding lead lag damper 40. This improves the folding performance of the rotor blade 30, in other words, the degree of freedom in the folding operation. FIG. 12 shows the rotor blade 30 rotated in a direction away from the corresponding lead lag damper 40. FIG. 13 shows the rotor blade 30 rotated in a direction toward the corresponding lead lag damper 40. It can be seen from FIG. 13 that the rotor blade 30 can be rotated without interfering with the lead lag damper 40.

[0037] 7 and 11 , in this embodiment, the first damper body 41 and the second damper body 42 are located closer to the head body 21 in the pitch axis direction AX3d than the first connecting member 24 and are located so as to overlap with the second through holes 46, 47, in other words, the lead lug fasteners 60 inserted in the second through holes 46, 47, as viewed in the pitch axis direction AX3d. According to this configuration, the first damper body 41 and the second damper body 42 are located closer to the pitch axis AX3. As a result, when folding the rotor blade 30, the user can rotate the rotor blade 30 by a large angle without interference with the first damper body 41 and the second damper body 42.

[0038] 2 and 3 show a state in which one of the three rotor blades 30 is at a rotational angle position of the rotor head 20 extending toward the rear of the airframe 11, and the remaining two rotor blades 30 are folded toward the rear. One of the remaining two rotor blades 30 is folded in a direction away from the corresponding lead lag damper 40, and the other is folded in a direction toward the corresponding lead lag damper 40. A user can fold the rotor blade 30 at a large angle in both the direction away from the corresponding lead lag damper 40 and the direction toward the corresponding lead lag damper 40, and therefore the rotor blade 30 can be folded compactly regardless of the rotational angle position of the rotor head 20. Therefore, a user does not need to strictly position the rotational angle position of the rotor head 20 when folding the rotor blade 30.

[0039] Furthermore, the head body 21 of the rotor blade assembly 15 is connected to the rotor blades 30 via two members, namely, a first connecting member 24 and a second connecting member 25. Therefore, the designer of the rotor blade assembly 15 can select an optimal material for the first connecting member 24 for connection related to rotation about the lead-lag hinge axis AX2, and can select an optimal material for the second connecting member 25 for connection related to rotation about the pitch axis AX3. In other words, the designer of the rotor blade assembly 15 can use the optimal material for each of the two types of rotation-related members. Specifically, the designer of the rotor blade assembly 15 can design dimensions and select a material for the first connecting member 24 that ensures wear resistance against sliding and also ensures strength with a small diameter for connection of the feathering hinge. Meanwhile, the designer of the rotor blade assembly 15 can design dimensions and select a material for the second connecting member 25 that can withstand the load acting on the rotor blades 30 while achieving weight reduction.

[0040] Furthermore, in the rotor blade assembly 15, the lead-lag damper 40 is connected to the rotor head 20 by the first rotor head connecting portion 48 and the second rotor head connecting portion 49 that are spaced apart in the pitch axis direction AX3d. Therefore, in the rotor blade assembly 15, the moment load associated with the lead-lag motion can be supported more stably than in a configuration in which the lead-lag damper 40 is connected to the rotor head 20 at a single point.

[0041] Furthermore, in the rotor blade assembly 15, the blade connecting portion 43 for connecting the lead lag damper 40 to the rotor blade 30 includes arms 44, 45 spaced apart in the lead lag hinge axial direction AX2d at a distance greater than the thickness of the base portion 31 of the rotor blade 30. This allows for weight reduction while maintaining the strength of the blade connecting portion 43. In addition, the user can use the space between the arms 44 and 45 as movement space for the rotor blade 30 when folding the rotor blade 30 toward the corresponding lead lag damper 40, as shown in FIG.

[0042] Furthermore, in the rotor blade assembly 15, the arms 44, 45 are connected to the first base 50 and the second base 51, respectively, so as to sandwich the first base 50 and the second base 51 in the stacking direction. Therefore, when lead-lag movement occurs, the rotor blade assembly 15 can transmit a displacement load to the first base 50 and the second base 51 via the first rotor head connecting portion 48 with a simple configuration.

[0043] Although the embodiments have been described above, the above-described embodiments are intended to facilitate understanding of the present teachings and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof. Furthermore, any combination or omission of each component described in the claims and specification is possible within the scope of solving at least part of the above-described problems or achieving at least part of the effects.

[0044] Furthermore, the above-described embodiment is not limited to helicopters, but can be applied to any rotorcraft having a main rotor with a lead-lag damper, such as a helicopter-type drone.

[0045] The present invention can be realized as the following aspects: The various aspects described below are not essential to the present invention and can be arbitrarily combined with any other embodiment.

[0046] According to a first aspect, a rotor blade assembly is provided. The rotor blade assembly includes a rotor head, a rotor blade, a lead lag damper, and a lead lag fastener. The rotor head has a rotor rotation axis and a lead lag hinge axis. The rotor blade is coupled to the rotor head to rotate about the lead lag hinge axis relative to the rotor head and has a base defining a first through hole. The lead lag damper has a damper body located closer to the rotor rotation axis than the base of the rotor blade when viewed in the direction of the rotor rotation axis, a blade connection portion defining a second through hole and coupled to the rotor blade, and a first rotor head connection portion coupled to the rotor head. The lead lag fastener is inserted into the first through hole and the second through hole, and connects the rotor blade to the blade connection portion of the lead lag damper.

[0047] According to a second aspect, in the first aspect, at least a portion of the blade connection portion of the lead-lag damper is located farther from the rotor rotational axis than the damper body as viewed in the rotor rotational axis direction. The blade connection portion extends from the base of the rotor blade to the damper body. According to the second aspect, the damper body and the rotor blade can be connected via an efficient path.

[0048] According to a third aspect, the rotor head of the first or second aspect includes a head body, a first connecting member, and a second connecting member. The first connecting member is connected to the rotor blade so that the rotor blade rotates about the lead-lag hinge axis. The second connecting member is connected to the first connecting member and to the head body so that the rotor blade rotates about a pitch axis that is perpendicular to the lead-lag hinge axis with respect to the head body. According to the third aspect, an optimal material for connection related to rotation about the lead-lag hinge axis can be selected for the first connecting member, and an optimal material for connection related to rotation about the pitch axis can be selected for the second connecting member. In other words, optimal materials can be used for each of the two types of rotational components.

[0049] According to a fourth aspect, in any one of the first to third aspects, the first connecting member, the second connecting member, and the first rotor head connecting portion are fastened together with a fastener, thereby connecting the first connecting member and the second connecting member and connecting the rotor head and the first rotor head connecting portion. According to the fourth aspect, the device configuration can be simplified and the number of parts can be reduced.

[0050] According to a fifth aspect, in any one of the first to fourth aspects, the lead-lag damper includes a second rotor head connection portion spaced apart from the first rotor head connection portion in the pitch axis direction perpendicular to the lead-lag hinge axis, thereby making it possible to stably support moment loads associated with lead-lag motion.

[0051] According to a sixth aspect, in any of the first to fifth aspects, the blade connection portion of the lead-lag damper includes a pair of arms each defining a second through hole. The pair of arms are spaced apart in the axial direction of the lead-lag hinge by a distance greater than the thickness of the base of the rotor blade. According to the sixth aspect, the rotor blade can be rotated toward the damper body through the pair of arms when folded while ensuring the strength of the blade connection portion.

[0052] According to a seventh aspect, in any of the first to sixth aspects, the damper body includes a first damper body and a second damper body disposed at a position sandwiching the first rotor head connection portion between the first damper body and the second damper body. The lead-lag damper further includes a first base, a second base, and a pressing member. The first base and the second base are disposed at a distance from each other so as to sandwich the first damper body, the first rotor head connection portion, and the second damper body in a direction in which the first damper body, the rotor head connection portion, and the second damper body overlap, and are respectively connected to the blade connection portion. The pressing member presses the first base and the second base in a direction in which they approach each other. According to the seventh aspect, the first damper body and the second damper body are pressed against the first base and the second base, respectively, by the pressing member, so that when a lead-lag movement occurs, the first damper body and the second damper body undergo shear deformation relative to the first base and the second base, generating an appropriate shear load and damping the lead-lag movement.

[0053] According to an eighth aspect, in any one of the first to seventh aspects, the blade connection portion includes a pair of arms each defining a second through hole. The pair of arms are spaced apart in the lead-lag hinge axial direction by a distance greater than the thickness of the base of the rotor blade. The pair of arms are connected to the first base and the second base, respectively, so as to sandwich the first base and the second base in a direction perpendicular to the pressing direction of the pressing member. According to the eighth aspect, when lead-lag movement occurs, shear deformation can be transmitted to the first base and the second base via the blade connection portion with a simple configuration.

[0054] According to a ninth aspect, in any one of the first to eighth aspects, the lead lag fastener includes a bolt and a bushing. The bolt has a tip portion with an external thread portion and is inserted into the first through hole and the second through hole. The bushing has an internal thread portion that meshes with the external thread portion and is partially disposed within the second through hole and fixed to the blade connecting portion. According to the ninth aspect, the rotor blade and the blade connecting portion of the lead lag damper can be connected without using a nut. This reduces the number of parts and eliminates the risk of losing the nut.

[0055] According to a tenth aspect, in any of the first to ninth aspects, the damper body is located closer to the head body in the pitch axis direction than the first connecting member. According to the tenth aspect, when the rotor blades are folded, the rotor blades can be rotated a large angle without interfering with the damper body. [Explanation of symbols]

[0056] 10...Helicopter 11...Aircraft 12...Rotor shaft 15...Rotor blade assembly 20...Rotor head 21...Head body 22...Base 23...extension part 24...First connecting member 24a...base 24b...Upper blade connecting member 24c...Lower blade connecting member 25...Second connecting member 26, 27, 28, 29...Fasteners 30...Rotor blade 31...Base 32...First through hole 33...Lead-lag damper connection 40...Lead-lag damper 41...First damper body 41a...Convex part 41b...Aperture 42...Second damper body 42a...Convex part 42b...Aperture 43...Blade connection part 44,45...Arm 46, 47...Second through hole 48...First rotor head connection 48a...Part 1 148a...Aperture 48b...Second part 49...Second rotor head connection 50...First Base 50a...convex part 50b...Aperture 51...Second Base 51a...Convex part 51b...Aperture 52...Pressing member 60...Lead lug fastener 61...Volts 63...Tip 64...Bushing 65...female thread 66...Retaining pin AX1...Rotor rotation axis AX2...Lead-lag hinge axis AX3...Pitch axis

Claims

1. 1. A rotor blade assembly comprising: a rotor head having a rotor rotation axis and a lead lag hinge axis; a rotor blade coupled to the rotor head for rotation relative to the rotor head about the lead-lag hinge axis, the rotor blade having a base defining a first through hole; a lead-lag damper including: a damper body located at a position closer to the rotor rotational axis than the base of the rotor blade as viewed in the rotor rotational axis direction; a blade connection portion defining a second through hole and connected to the rotor blade; and a first rotor head connection portion connected to the rotor head; a lead lag fastener inserted into the first through hole and the second through hole and connecting the rotor blade and the blade connecting portion of the lead lag damper; 1. A rotor blade assembly comprising:

2. 2. The rotor blade assembly of claim 1, At least a portion of the blade connection portion of the lead-lag damper is located at a position farther from the rotor rotational axis than the damper body when viewed in the rotor rotational axis direction, and the blade connection portion extends from the base of the rotor blade to the damper body. Rotor blade assembly.

3. 3. A rotor blade assembly according to claim 1 or claim 2, The rotor head includes: A head body, a first connecting member connected to the rotor blade for rotation about the lead-lag hinge axis; a second connecting member connected to the first connecting member and connected to the head body so as to rotate about a pitch axis perpendicular to the lead-lag hinge axis with respect to the head body; Contains Rotor blade assembly.

4. 4. The rotor blade assembly of claim 3, The first connecting member, the second connecting member, and the first rotor head connecting portion are fastened together with a fastener, thereby connecting the first connecting member and the second connecting member and connecting the rotor head and the first rotor head connecting portion. Rotor blade assembly.

5. 3. A rotor blade assembly according to claim 1 or claim 2, The lead lag damper includes a second rotor head connection portion spaced apart from the first rotor head connection portion in a pitch axis direction perpendicular to the lead lag hinge axis. Rotor blade assembly.

6. 3. A rotor blade assembly according to claim 1 or claim 2, the blade connection portion of the lead-lag damper includes a pair of arms each defining the second through hole; The pair of arms are spaced apart in the axial direction of the lead-lag hinge at a distance greater than the thickness of the base of the rotor blade. Rotor blade assembly.

7. 3. A rotor blade assembly according to claim 1 or claim 2, the damper body includes a first damper body and a second damper body disposed at a position where the first rotor head connecting portion is sandwiched between the first damper body and the second damper body, The lead lag damper further comprises: a first base and a second base that are spaced apart from each other so as to sandwich the first damper body, the first rotor head connecting portion, and the second damper body in a direction in which the first damper body, the rotor head connecting portion, and the second damper body overlap, and that are connected to the blade connecting portion, respectively; a pressing member that presses the first base and the second base in directions in which they approach each other; have Rotor blade assembly.

8. 8. The rotor blade assembly of claim 7, the blade connecting portion includes a pair of arms each defining the second through hole; the pair of arms are spaced apart in the axial direction of the lead-lag hinge by a distance greater than a thickness of the base of the rotor blade; The pair of arms are connected to the first base and the second base, respectively, so as to sandwich the first base and the second base in a direction perpendicular to the pressing direction of the pressing member. Rotor blade assembly.

9. 3. A rotor blade assembly according to claim 1 or claim 2, The lead lug fastener is a bolt including a tip portion having a male thread portion and inserted into the first through hole and the second through hole; a bushing having an internal thread portion that threadably engages with the external thread portion, the bushing being partially disposed within the second through hole and fixed to the blade connecting portion. Rotor blade assembly.

10. 4. The rotor blade assembly of claim 3, The damper body is located closer to the head body in the pitch axis direction than the first connecting member. Rotor blade assembly.

11. 1. A rotor blade assembly comprising: a rotor head having a rotor rotation axis and a lead lag hinge axis; a rotor blade coupled to the rotor head for rotation relative to the rotor head about the lead-lag hinge axis, the rotor blade having a base defining a first through hole; a lead-lag damper including a damper body, a blade connection portion that defines a second through hole and is connected to the rotor blade, and a rotor head connection portion that is connected to the rotor head; a lead lag fastener inserted into the first through hole and the second through hole and connecting the rotor blade and the blade connecting portion of the lead lag damper; Equipped with With the lead lag fastener removed from the first through hole and the second through hole, the rotor blade rotates about the lead lag hinge axis toward the opposite side from the lead lag damper by a predetermined angle, and the rotor blade rotates about the lead lag hinge axis toward the lead lag damper by the predetermined angle without interfering with the lead lag damper. Rotor blade assembly.

12. 1. A rotorcraft comprising: A rotor blade assembly according to any one of claims 1, 2 and 11. Rotorcraft.

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