Rotor assembly and rotorcraft

Abstract

To provide a rotor assembly in which the influence of a centrifugal force acting on a scissors link on a pitch operation force is reduced.SOLUTION: A rotor assembly for a rotary wing aircraft includes a rotor shaft rotating about a rotor axis, a hub coupled to the rotor shaft and rotating about the rotor axis, the hub having a blade coupling rotating about a pitch axis, a blade coupled to the blade coupling, a sliding sleeve, a pitch link coupling a rotating portion of the sliding sleeve to the blade coupling, a first coupling rotatably coupled to the rotating portion about a first rotational axis non-parallel to the rotor axis, and a second coupling rotatably coupled to the hub or the rotor shaft about a second rotational axis parallel to the first rotational axis, and a counterweight attached to the scissors link.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] A typical helicopter tail rotor assembly employs a system for varying its thrust by changing its pitch. Specifically, a link mechanism called a pitch link is connected to the blades, which rotate in conjunction with the rotation of the tail rotor shaft (also known as the mast). The blades are configured to rotate about a pitch axis. The pitch link is connected to a sliding sleeve that slides along the tail rotor shaft. More specifically, the sliding sleeve includes a non-rotating portion that does not rotate about the tail rotor rotation axis and a rotating portion that is connected to the tail rotor shaft. The non-rotating portion is connected to an actuator, and the entire sliding sleeve slides along the tail rotor shaft. A pitch link is connected to this rotating portion. Therefore, as the sliding sleeve slides, the pitch of the blades is changed. In addition to the pitch link, the rotating portion is further connected to the blades via a link called a scissors. The scissors transmit the rotational motion of the tail rotor shaft to the rotating portion, and expand and contract as the sliding sleeve slides. In Patent Document 1 below, the extension and contraction is achieved by employing flexible scissors. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-69296 Summary of the Invention [Problem to be solved by the invention]

[0004] When the extension and retraction of the scissors described above is achieved by a link mechanism also known as a scissors link, centrifugal force acts on the scissors link when the scissors link rotates together with the tail rotor shaft. This centrifugal force acts to move the scissors link outward from the center of the tail rotor shaft, i.e., acts as a load in a direction that bends the scissors link, and affects the force used by the actuator to slide the sliding sleeve toward the hub, i.e., the pitch control force. For these reasons, it is expected to provide a rotor assembly in which the effect of centrifugal force acting on the scissors link on the pitch control force is reduced. [Means for solving the problem]

[0005] This specification discloses a rotor assembly for a rotorcraft. The rotor assembly includes a rotor shaft, a hub, blades, a sliding sleeve, a pitch link, a scissors link, and a counterweight. The rotor shaft has a rotor axis and rotates about the rotor axis. The hub has a pitch axis non-parallel to the rotor axis and is connected to the rotor shaft and rotates about the rotor axis. The hub has a blade connection portion that rotates about the pitch axis. The blades are connected to the blade connection portion. The sliding sleeve has a rotating portion connected to the rotor shaft to be slidable along the rotor axis and a non-rotating portion that does not rotate relative to the rotor axis and slides along the rotor axis together with the rotating portion. The pitch link connects the rotating portion to the blade connection portion. The scissor link has a first connecting portion connected to the rotating portion so as to be rotatable about a first rotation axis that is not parallel to the rotor axis, and a second connecting portion connected to the hub or rotor shaft so as to be rotatable about a second rotation axis that is parallel to the first rotation axis. The counterweight is attached to the scissor link.

[0006] According to this rotor assembly, the designer of the rotor assembly can easily design a rotor assembly in which the centrifugal force acting on the scissors linkage has little effect on the pitch control force. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of a helicopter according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a tail rotor assembly. [Figure 3] FIG. 3 is a partially enlarged view of FIG. 2. [Figure 4] FIG. 2 is a partially enlarged perspective view of the tail rotor assembly according to the first embodiment. [Figure 5] FIG. 5 is a partially enlarged perspective view of a tail rotor assembly according to a comparative example, corresponding to FIG. 4. [Figure 6] FIG. 2 is a perspective view of a tail rotor assembly. [Figure 7] FIG. 7 is a cross-sectional view taken along line AA in FIG. 6. [Figure 8] FIG. 10 is a side view of the scissor linkage in the most extended relative position. [Figure 9] FIG. 10 is a side view of the scissors linkage in the most bent relative position. [Figure 10] FIG. 10 is a side view of a scissor linkage in an intermediate relative position. [Figure 11] FIG. 10 is a schematic diagram of a scissors linkage according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A helicopter 10 according to a first 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, but it may also be a manned aircraft. As shown in FIG. 1 , the helicopter 10 includes an airframe 11, a main rotor assembly 14, and a tail rotor assembly 20. The airframe 11 includes a fuselage section 12 and a tail section 13 that extends rearward from the fuselage section 12 in an elongated manner. The main rotor assembly 14 is disposed above the fuselage section 12. The tail rotor assembly 20 is disposed at the rear end of the tail section 13. The tail rotor assembly 20 generates a torque to cancel out a counter torque acting on the airframe 11 when the blades of the main rotor assembly 14 rotate.

[0009] As shown in Figures 2 and 3, the tail rotor assembly 20 includes a tail rotor shaft 30, a hub 40, two blades 50, a sliding sleeve 60, two pitch links 70, two scissor links 80, and a plurality of counterweights 90. Hereinafter, the tail rotor shaft 30 will be simply referred to as the rotor shaft 30. The rotor shaft 30 extends in a direction perpendicular to the direction in which the tail section 13 extends. The rotor shaft 30 has a rotor axis AX1 and rotates around the rotor axis AX1. In this specification, the term "axis" refers to an imaginary line representing the center of rotation.

[0010] As shown in FIGS. 2 and 3 , the hub 40 includes a hub axle 41, two blade connecting portions 42, and two connecting portions 44. The hub axle 41 has a pitch axis AX2. The pitch axis AX2 coincides with the center axis of the hub axle 41, which extends in the longitudinal direction of the hub axle 41. The pitch axis AX2 is not parallel to the rotor axis AX1 and, in this embodiment, is substantially perpendicular to the rotor axis AX1. Two blade connecting portions 42 are attached to both ends of the hub axle in the longitudinal direction. The blade connecting portions 42 rotate relative to the hub axle 41 about the pitch axis AX2. A blade 50 is fixed to the longitudinal tip of each blade connecting portion 42. The blade connecting portions 42 and the blades 50 rotate together, thereby changing the pitch angle of the blades 50.

[0011] As shown in Figures 2, 3, and 6, each of the coupling portions 44 couples the tip end of the rotor shaft 30 to the hub shaft 41. Specifically, as shown in Figure 3, the rotor shaft 30 has two rotor shaft coupling portions 31 extending radially outward from the tip end of the rotor shaft 30 relative to the rotor axis AX1. Two coupling portions 44 are coupled to the two rotor shaft coupling portions 31, respectively. As shown in Figures 3 and 6, each of the two rotor shaft coupling portions 31 extends from the rotor shaft 30 in a direction away from the rotor axis AX1, then bends and extends toward the hub shaft 41, and is coupled to the coupling portion 44 of the hub shaft 41. With this configuration, the hub 40 and the blades 50 rotate together with the rotor shaft 30 about the rotor axis AX1.

[0012] As shown in Fig. 6, counterweights 43 are attached to each blade connecting portion 42 at two locations. The counterweights 43 are provided to adjust the pitch control force on the hub 40 side. For each blade connecting portion 42, the two counterweights 43 are located at different circumferential positions relative to the pitch axis AX2.

[0013] As shown in FIGS. 3, 4, and 6, the sliding sleeve 60 includes a rotating portion 61 and a non-rotating portion 62. As shown in FIG. 7, the rotating portion 61 has a cylindrical portion 65 arranged to surround the rotor shaft 30 in the circumferential direction. The rotating portion 61 is connected to the rotor shaft 30 by inserting the rotor shaft 30 into the cylindrical portion 65. The rotating portion 61 is slidable along the rotor axis AX1. For reasons described below, the rotating portion 61 rotates together with the rotor shaft 30 about the rotor axis AX1. The non-rotating portion 62 surrounds the outer periphery of the cylindrical portion 65 of the rotating portion 61 and is connected to the rotating portion 61 via a bearing 64 shown in FIG. 7. The non-rotating portion 62 does not rotate about the rotor axis AX1 but slides along the rotor axis AX1 together with the rotating portion 61. As shown in FIGS. 3 and 6, the rotating portion 61 is connected to an actuator 63 by a link mechanism. The sliding movement of the sliding sleeve 60 is performed by driving the actuator 63. The actuator 63 is controlled by a controller that includes a processor.

[0014] As shown in FIGS. 3, 4, and 6, each of the two pitch links 70 connects the rotating portion 61 of the sliding sleeve 60 to the blade connecting portion 42 of the hub 40. Specifically, the rotating portion 61 has two rotating-portion-side connecting portions 66 extending from the cylindrical portion 65 in a direction intersecting the rotor axis AX1. One ends of the two pitch links 70 are respectively connected to the two rotating-portion-side connecting portions 66 so as to be rotatable relative to each other, and the other ends of the two pitch links 70 are respectively connected to the two blade connecting portions 42 so as to be rotatable relative to each other. When the sliding sleeve 60 slides along the rotor axis AX1, the displacement of the sliding sleeve 60 is transmitted to the blade connecting portion 42 via the pitch link 70. This causes the blade connecting portion 42 and the blades 50 to rotate about the pitch axis AX2 relative to the hub shaft 41, thereby changing the pitch angle.

[0015] As shown in Figures 3, 4, 6, and 7, each of the two scissors links 80 connects the rotating portion 61 of the sliding sleeve 60 and the rotor shaft 30. Specifically, the scissors link 80 includes a lower link 81 and an upper link 82. The upper link 82 is located closer to the hub shaft 41 than the lower link 81. As shown in Figures 3, 4, 6, 7, and 8, the lower link 81 includes a first connecting portion 83 and a third connecting portion 85. The upper link 82 includes a second connecting portion 84 and a fourth connecting portion 86. As shown in Figures 3 and 7, the two scissors links 80 are positioned 180 degrees rotationally symmetrical about the rotor axis AX1.

[0016] As shown in FIGS. 3, 7, and 8, the first connecting portion 83 of the lower link 81 is connected to the rotating portion 61 of the sliding sleeve 60 so as to be rotatable about a first rotation axis AX3. In this embodiment, the first connecting portion 83 and the rotating portion 61 are connected using a bolt and a nut. The first rotation axis AX3 is non-parallel to the rotor axis AX1 and is perpendicular to a predetermined plane including the rotor axis AX1. The second connecting portion 84 of the upper link 82 is connected to the scissors connecting portion 32 of the rotor shaft 30 so as to be rotatable about a second rotation axis AX4. In this embodiment, the second connecting portion 84 and the scissors connecting portion 32 are connected using a bolt and a nut. The second rotation axis AX4 is parallel to the first rotation axis AX3. The third connecting portion 85 of the lower link 81 is connected to the fourth connecting portion 86 of the upper link 82 so as to be rotatable about a third rotation axis AX5. In this embodiment, the third connecting portion 85 and the fourth connecting portion 86 are connected using bolts and nuts. The third rotation axis AX5 is parallel to the first rotation axis AX3.

[0017] When the sliding sleeve 60 slides along the rotor axis AX1, the scissors link 80 expands and contracts and deforms. When the sliding sleeve 60 slides in a direction away from the hub 40, the scissors link 80 extends. In other words, at this time, the scissors link 80 deforms so that the first rotation axis AX3 and the second rotation axis AX4 move away from each other. When the sliding sleeve 60 slides in a direction toward the hub 40, the scissors link 80 bends. In other words, at this time, the scissors link 80 deforms so that the first rotation axis AX3 and the second rotation axis AX4 move closer to each other. Figure 8 shows the scissors link 80 in a relative position where the first rotation axis AX3 and the second rotation axis AX4 are furthest apart within the relative movable range of the lower link 81 and the upper link 82. Within the relative movable range of the lower link 81 and the upper link 82, the relative position where the first rotation axis AX3 and the second rotation axis AX4 are furthest apart is hereinafter referred to as the most extended relative position. Fig. 9 shows the scissors link 80 at a relative position where the first rotation axis AX3 and the second rotation axis AX4 are closest within the relative movable range of the lower link 81 and the upper link 82. Within the relative movable range of the lower link 81 and the upper link 82, the relative position where the first rotation axis AX3 and the second rotation axis AX4 are closest is hereinafter referred to as the most bent relative position. Fig. 10 shows the scissors link 80 at an intermediate relative position between the most extended relative position and the most bent relative position.

[0018] In this embodiment, the relative movement range between the lower link 81 and the upper link 82, in other words, the most extended relative position and the most bent relative position, is determined by the control of a controller that drives the actuator 63. In other words, the range over which the sliding sleeve 60 can slide is determined by the possible values ​​of the control parameters of the controller. However, the relative movement range can be determined in any manner. For example, the relative movement range may be determined by the structural maximum movement range of the actuator 63. Alternatively, the relative movement range may be determined by a stopper that abuts against the sliding sleeve 60 to restrict the movement of the sliding sleeve 60.

[0019] When the hub 40 and the blades 50 rotate in accordance with the rotation of the rotor shaft 30, the rotational motion is transmitted to the rotating portion 61 of the sliding sleeve 60 via the scissors link 80. That is, the scissors link 80 can transmit the rotation of the rotor shaft 30 to the rotating portion 61 while expanding and contracting and deforming according to the sliding position of the sliding sleeve 60. As a result, the rotating portion 61 rotates together with the rotor shaft 30. Note that the second connecting portion 84 of the upper link 82 may be connected to the hub 40 so as to be rotatable about the second rotation axis AX4. In this case, the scissors link 80 can transmit the rotation of the rotor shaft 30 to the rotating portion 61 via the hub 40 while expanding or bending according to the sliding position of the sliding sleeve 60.

[0020] A counterweight 90 is removably attached to each of the scissors links 80. Specifically, as shown in Fig. 8, the upper link 82 has an attachment portion 87 for attaching the counterweight 90. The attachment portion 87 is a portion that is closer to the hub axle 41 in the rotor axial direction than the second connecting portion 84 and farther from the rotor axis AX1 than the second connecting portion 84. The rotor axial direction is the direction in which the rotor axis AX1 extends.

[0021] As shown in FIG. 8 , the counterweight 90 is attached so that it is sandwiched between the head of a bolt 91 and an attachment portion 87. The bolt 91 has a shaft and a head located at one end of the shaft. In this embodiment, the counterweight 90 has a disk-shaped main body and an opening that penetrates the disk-shaped main body in the thickness direction. The attachment portion 87 has a through hole 88 that extends in the direction of the second rotation axis AX4 and a through hole 89 that extends perpendicular to the direction of the second rotation axis AX4. The through hole 88 is used to tighten a nut 92 disposed in the through hole. A user fixes the counterweight 90 to the attachment portion 87 by inserting the shaft of the bolt 91 through the counterweight 90 and the through hole 89 and tightening the nut 92. Although two counterweights 90 are attached to the attachment portion 87 in FIG. 8 , the number of counterweights 90 attached to the attachment portion 87 is not limited to this. The number of counterweights 90 may be one, or three or more. The bolt 91 may have a hole that penetrates radially through the bolt 91. The nut 92 may be a grooved nut. A cotter pin may be attached so that it passes through the groove of the nut 92 and the hole of the bolt 91. This prevents the nut 92 from falling off. In this embodiment, the counterweight 90 and the upper link 82 are fastened together by the bolt 91 and the nut 92, but the embodiment is not limited to this. For example, the upper link may be a single component that has a portion that functions as a counterweight.

[0022] The counterweight 90 is located on the opposite side of the first rotation axis AX3 with respect to the second rotation axis AX4 in the rotor axial direction. Mounting the counterweight 90 at this position effectively offsets the centrifugal force acting on the joint of the scissors link 80, i.e., the connection between the third connecting portion 85 and the fourth connecting portion 86, during rotation of the rotor shaft 30. Specifically, centrifugal force acts on the joint of the scissors link 80 in the direction indicated by arrow A1 in FIG. 8 . This centrifugal force bends and deforms the scissors link 80, displacing the rotating portion 61 of the sliding sleeve 60 and the pitch link 70 toward the hub 40, which unintentionally affects the pitch control force. In other words, the centrifugal force acting in the direction indicated by arrow A1 acts to rotate the upper link 82 of the scissors link 80 clockwise on the page about the second rotation axis AX4. However, by providing the counterweight 90, centrifugal force acts in the direction indicated by arrow A2 in Figure 8. In other words, the centrifugal force in the direction indicated by arrow A2 acts to rotate the upper link 82 of the scissors link 80 counterclockwise on the page about the rotation axis AX4. That is, this rotational force acts in a direction that stretches and deforms the scissors link 80. Therefore, the two forces cancel each other out, reducing the unintended effect of the centrifugal force on the pitch control force. This allows the designer of the tail rotor assembly 20 to easily design a tail rotor assembly 20 in which the effect of the centrifugal force on the scissors link 80 on the pitch control force is reduced.

[0023] Furthermore, according to this embodiment, the weight of the entire tail rotor assembly 20 can be reduced. FIG. 5 shows a tail rotor assembly 120 according to a comparative example and corresponds to FIG. 4. Among the components of the tail rotor assembly 120, the same components as those of the tail rotor assembly 20 according to this embodiment are denoted by the same reference numerals as in FIG. 4. As can be seen from a comparison between FIGS. 4 and 5, the tail rotor assembly 120 differs from the tail rotor assembly 20 in that it includes a scissors link 180 instead of the scissors link 80 and a counterweight 143 instead of the counterweight 43. The counterweight 90 is not attached to the scissors link 180. The counterweight 143 needs to be significantly larger in size and weight than the counterweight 43 to suppress the pitch control force undesirably affected by the scissors link 180. In addition, components such as the pitch link 70 are present between the counterweight 143 and the scissors link 80, and these components must be stronger to transmit the countervailing loads, which may increase the weight of the components.

[0024] 5 can also compensate for the load in the direction of extension deformation caused by the centrifugal force acting on the joint of the scissors link 180. However, according to this embodiment, the counterweight 90 is provided, and the load in the direction of extension deformation caused by the centrifugal force is compensated for by the counterweight 90 alone. This allows the weight of the counterweight 43 to be significantly smaller than that of the counterweight 143, resulting in a reduction in the overall weight of the tail rotor assembly 20. In an alternative embodiment, the load in the direction of extension deformation caused by the centrifugal force may be compensated for by adjusting the weights of both the counterweight 90 and the counterweight 43.

[0025] 8 to 10 , regardless of the relative positions of the lower link 81 and the counterweight 90, the end of the shank of the bolt 91 opposite the head is located farther from the rotor axis AX1, or in other words, from the rotor shaft 30, than the head of the bolt 91. In other words, even when the lower link 81 and the counterweight 90 are in the most extended relative position, the end of the shank of the bolt 91 opposite the head is located farther from the rotor axis AX1 than the head of the bolt 91. According to this configuration, when the blades 50 and the hub 40 of the tail rotor assembly 20 are rotating, the acting centrifugal force always presses the bolt 91 in a direction from the head of the bolt 91 toward the end of the shank opposite the head, i.e., in a direction toward insertion into the through-hole 89 of the mounting portion 87. In other words, the acting centrifugal force presses the bolt 91 in a direction opposite to the direction in which it would drop out of the scissors link 80. Therefore, even if the nut 92 unintentionally falls off and the fastening force is lost while the tail rotor shaft 30 is rotating, the counterweight 90 and the bolt 91 will not fall off.

[0026] A scissors link 280 according to the second embodiment will be described below with reference to FIG. 11. As shown in FIG. 11, the scissors link 280 includes a lower link 281 and an upper link 282, similar to the first embodiment. The lower link 281 includes a first connecting portion 283 and a third connecting portion 285, and the upper link 282 includes a second connecting portion 284 and a fourth connecting portion 286. The first connecting portion 283, the third connecting portion 285, the second connecting portion 284, and the fourth connecting portion 286 correspond to the first connecting portion 83, the third connecting portion 85, the second connecting portion 84, and the fourth connecting portion 86 according to the first embodiment, respectively. The counterweight 90 is located on the opposite side of the first rotation axis AX3 from the second rotation axis AX4 in the rotor axial direction.

[0027] Even when the counterweight 90 is disposed in this position, when the rotor shaft 30 rotates and a rotational force acting counterclockwise on the page about the first rotation axis AX3 due to centrifugal force acts on the joint between the lower link 281 and the upper link 282 (in other words, a rotational force acting in a direction that bends the scissors link), the counterweight 90 acts to rotate clockwise on the page about the first rotation axis AX3 in a direction that offsets the centrifugal force (in other words, a rotational force acting in a direction that extends the scissors link). Therefore, as with the first embodiment, the designer of the tail rotor assembly 20 can easily design a tail rotor assembly 20 in which the pitch control force due to centrifugal force acting on the scissors link 280 is less affected. Note that, in this embodiment, the counterweight 90 and the lower link 281 are fastened together by the bolt 91 and the nut 92, but the embodiment is not limited to this. For example, the lower link may be a single component having a portion that functions as a counterweight.

[0028] 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.

[0029] For example, in the first embodiment, the counterweight 90 may be attached at any position and in any orientation as long as it can at least partially offset the rotational force in the direction in which the scissor link is bent due to the centrifugal force acting on the joint of the scissor link 80. This also applies to the second embodiment.

[0030] Furthermore, an elastic one-piece hub may be used instead of the hub 40 including the hub axle 41 and the blade connecting portion 42. In this case, the pitch of the blades is changed by elastic deformation of the hub.

[0031] The present invention can also be realized as the following embodiments. The various embodiments described below are not essential to the present invention and can be arbitrarily combined with any other embodiments.

[0032] According to a first aspect, there is provided a rotor assembly for a rotorcraft. The rotor assembly includes a rotor shaft, a hub, blades, a sliding sleeve, a pitch link, a scissors link, and a counterweight. The rotor shaft has a rotor axis and rotates about the rotor axis. The hub has a pitch axis non-parallel to the rotor axis and is connected to the rotor shaft and rotates about the rotor axis. The hub has a blade connection portion that rotates about the pitch axis. The blades are connected to the blade connection portion. The sliding sleeve has a rotating portion connected to the rotor shaft to be slidable along the rotor axis and a non-rotating portion that does not rotate relative to the rotor axis and slides along the rotor axis together with the rotating portion. The pitch link connects the rotating portion to the blade connection portion. The scissor link has a first connecting portion connected to the rotating portion so as to be rotatable about a first rotation axis that is not parallel to the rotor axis, and a second connecting portion connected to the hub or rotor shaft so as to be rotatable about a second rotation axis that is parallel to the first rotation axis. The counterweight is attached to the scissor link.

[0033] According to a second aspect, the scissors linkage of the first aspect includes a lower link having a first connecting portion and an upper link having a second connecting portion and connected to the lower link so as to be rotatable about a third rotation axis parallel to the first rotation axis. The counterweight is located on the opposite side of the second rotation axis from the first rotation axis in the rotor axial direction with respect to the second rotation axis. According to the second aspect, when the rotor shaft rotates and a rotational force due to centrifugal force acts on the joint between the lower link and the upper link in a direction that bends the scissors link, the counterweight acts to generate a rotational force about the second rotation axis in a direction that offsets the rotational force due to the centrifugal force, in other words, a rotational force in a direction that extends the scissors link. This reduces unintended effects of the centrifugal force on the pitch control force.

[0034] According to a third aspect, in the first or second aspect, the scissors linkage includes a lower link having a first connecting portion and an upper link having a second connecting portion and connected to the lower link so as to be rotatable about a third rotation axis parallel to the first rotation axis. The counterweight is located on the opposite side of the first rotation axis from the second rotation axis in the rotor axial direction with respect to the first rotation axis. According to the third aspect, when the rotor shaft rotates and a rotational force due to centrifugal force acts on the joint between the lower link and the upper link in a direction that bends the scissors link, the counterweight acts to generate a rotational force about the first rotation axis in a direction that offsets the rotational force due to centrifugal force, in other words, a rotational force in a direction that extends the scissors link. This reduces unintended effects of the centrifugal force on the pitch control force.

[0035] According to a fourth aspect, in any of the first to third aspects, the counterweight is attached to the upper link by a bolt having a shaft and a head located at one end of the shaft, and a nut, so that the counterweight is sandwiched between the head of the bolt and the upper link. When the lower link and the upper link are in a relative position where the first rotation axis and the second rotation axis are furthest apart within the relative range of movement of the lower link and the upper link caused by the sliding displacement of the sliding sleeve, the end of the bolt shank opposite the head is located farther from the rotor shaft than the head of the bolt. According to the fourth aspect, regardless of the tension state of the scissors link, in other words, regardless of the relative position of the lower link and the upper link, centrifugal force acting on the bolt presses the bolt in the direction of insertion, i.e., in the direction opposite to the bolt's removal direction. Therefore, even if the nut unintentionally comes off while the rotor shaft is rotating and the fastening force is lost, the counterweight and bolt will not come off. [Explanation of symbols]

[0036] 10...Helicopter 11...Aircraft 12...Torso 13...Tail section 14...Main rotor assembly 20,120...Tail rotor assembly 30...Tail rotor shaft 31...Rotor shaft connection part 32...Scissor joint 40...hub 41...hub axle 42...Blade connection part 43,143...Counterweight 44...Connection part 50...Blade 60...Sliding sleeve 61...Rotating part 62...Non-rotating part 63...Actuator 64...Bearing 65...Cylindrical part 66...Rotating part side connection part 70...Pitch link 80, 180, 280...Scissor link 81,281...Lower Link 82,282...Upper link 83,283...1st connection part 84,284...Second connection part 85,285...Third connection part 86,286...4th connection part 87...Mounting part 88,89...Through holes 90...Counterweight 91...Bolt 92...Nut AX1...Rotor axis AX2...Pitch axis AX3...First rotation axis AX4...second rotation axis AX5...Third rotation axis

Claims

1. 1. A rotor assembly for a rotorcraft, comprising: a rotor shaft having a rotor axis and rotating about the rotor axis; a hub connected to the rotor shaft and rotating about the rotor axis, the hub having a pitch axis non-parallel to the rotor axis, the hub having a blade connection portion rotating about the pitch axis; a blade connected to the blade connecting portion; a sliding sleeve including a rotating portion connected to the rotor shaft so as to be slidable along the rotor axis, and a non-rotating portion that does not rotate relative to the rotor axis and slides along the rotor axis together with the rotating portion; a pitch link connecting the rotating portion and the blade connecting portion; a scissors linkage having: a first connecting portion connected to the rotating portion so as to be rotatable about a first rotation axis that is not parallel to the rotor axis; and a second connecting portion connected to the hub or the rotor shaft so as to be rotatable about a second rotation axis that is parallel to the first rotation axis; a counterweight attached to the scissor link; A rotor assembly comprising:

2. 2. The rotor assembly of claim 1, the scissors linkage includes a lower link having the first connecting portion, and an upper link having the second connecting portion and connected to the lower link so as to be rotatable about a third rotation axis parallel to the first rotation axis, The counterweight is located on the opposite side of the second rotation axis from the first rotation axis in the rotor axial direction. Rotor assembly.

3. 2. The rotor assembly of claim 1, the scissors linkage includes a lower link having the first connecting portion, and an upper link having the second connecting portion and connected to the lower link so as to be rotatable about a third rotation axis parallel to the first rotation axis, The counterweight is located on the opposite side of the first rotation axis from the second rotation axis in the rotor axial direction. Rotor assembly.

4. 3. The rotor assembly of claim 2, the counterweight is attached to the upper link by a bolt having a shaft portion and a head portion located at one end of the shaft portion, and a nut such that the counterweight is sandwiched between the head portion of the bolt and the upper link; When the lower link and the upper link are in a relative position where the first rotation axis and the second rotation axis are furthest apart within a relative movable range of the lower link and the upper link caused by sliding displacement of the sliding sleeve, the end of the bolt shaft opposite to the head is located farther from the rotor shaft than the head of the bolt. Rotor assembly.

5. 1. A rotorcraft comprising: A rotor assembly according to any one of claims 1 to 4 is provided. Rotorcraft.

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