Landing device for rotary-winged aircraft and rotary-winged aircraft provided with same

Abstract

This landing device for a rotary-winged aircraft comprises: a fixed body that is fixed to a fuselage of the rotary-winged aircraft; a support body that includes at least one ground contact body contacting a landing surface when the rotary-winged aircraft is in a non-flight state; at least one spring that connects the fixed body and the support body in a manner allowing the fixed body and the support body to move relative to each other, and is for reducing, together with the support body, vibration of the fuselage of the rotary-winged aircraft when the rotary-winged aircraft is in a flight state; and a rigid body that moves relative to at least one of the fixed body and the support body, between a restricting position where the same restricts the fixed body and the support body from approaching each other, and a release position where the same releases the restriction of the fixed body and the support body from approaching each other.

Description

Landing gear for rotorcraft and rotorcraft equipped with same

[0001] The present disclosure relates to a landing gear for a rotorcraft and a rotorcraft including the same.

[0002] Rotary-wing aircraft such as helicopters fly by obtaining lift through the rotation of their rotors. For example, Patent Document 1 discloses a helicopter equipped with a vibration reduction device that reduces vibrations caused by the rotation of the rotors. The vibration reduction device disclosed in Patent Document 1 includes a spring and an actuator. The spring and actuator are arranged in the middle of each support leg that connects the lower end of the fuselage to the landing gear skid. The vibration reduction device has the landing gear skid as a mass that reduces helicopter vibration.

[0003] Japanese Patent Application Publication No. 11-348893

[0004] The rotary wing aircraft with vibration reduction function disclosed in Patent Document 1 has room for improvement in terms of, for example, the vibration reduction function or the strength of the landing gear.

[0005] An object of the present disclosure is to provide an improved landing gear for a rotary wing aircraft and a rotary wing aircraft equipped with the same.

[0006] A landing gear for a rotary-wing aircraft according to one aspect of the present disclosure comprises a support including a fixed body fixed to a fuselage of the rotary-wing aircraft and at least one ground contact body that contacts a landing surface when the rotary-wing aircraft is not in a flying state; at least one spring that connects the fixed body and the support so that the fixed body and the support can move relative to each other, and that reduces vibration of the fuselage of the rotary-wing aircraft together with the support when the rotary-wing aircraft is in a flying state; and a rigid body that moves relative to at least one of the fixed body and the support between a restricting position that restricts the fixed body and the support from approaching each other and a releasing position that releases the restriction on the fixed body and the support from approaching each other.

[0007] A landing gear for a rotary-wing aircraft according to another aspect of the present disclosure comprises a support including a fixed body fixed to a fuselage of the rotary-wing aircraft and at least one ground contact body that contacts a landing surface when the rotary-wing aircraft is not in flight, and at least one spring that connects the fixed body and the support so that the fixed body and the support can move relative to each other, and that reduces vibration of the fuselage of the rotary-wing aircraft together with the support when the rotary-wing aircraft is in flight, the at least one spring including a spring that vibrates in a direction different from the up and down direction.

[0008] A rotary-wing aircraft according to one aspect of the present disclosure comprises a fuselage, at least one rotor blade supported by the fuselage, and any one of the landing gears described above.

[0009] According to the present disclosure, it is possible to provide an improved landing gear for a rotary-wing aircraft and a rotary-wing aircraft equipped with the same.

[0010] 11 . FIG. 12 is a schematic side view of a rotary-wing aircraft equipped with a landing gear according to a first embodiment. FIG. 13 is a perspective view of the landing gear of the rotary-wing aircraft of FIG. 1. FIG. 14 is an enlarged side view of the vicinity of a spring and a rigid body in the landing gear of FIG. 2. FIG. 15 is an enlarged front view of the vicinity of a spring and a rigid body in the landing gear of FIG. 2. FIG. 16 is a schematic diagram showing a state in which the rigid body is in a restricted position. FIG. 17 is a schematic diagram showing a state in which the rigid body is in a released position. FIG. 18 is a block diagram showing a control system for moving the rigid body. FIG. 19 is a flowchart showing the control flow of a controller. FIG. 19 is a schematic diagram showing a state in which the rigid body is in a restricted position in a first modified example of the first embodiment. FIG. 19 is a schematic diagram showing a state in which the rigid body is in a released position in a first modified example of the first embodiment. FIG. 19 is a schematic diagram showing a state in which the rigid body is in a released position in a second modified example of the first embodiment. FIG. 19 is a perspective view of a lower part of the rigid body in the second modified example of the first embodiment. FIG. 19 is a cross-sectional view taken along arrows XIII-XIII in FIG. 11 . FIG. 19 is a schematic diagram showing a state in which the rigid body is in a released position in a third modified example of the first embodiment. FIG. 10 is a schematic diagram showing a state in which the rigid body is in a release position in a fourth modified example of the first embodiment. FIG. 11 is a schematic diagram showing a state in which the rigid body is in a restriction position in a fourth modified example of the first embodiment. FIG. 12 is a schematic diagram showing a state in which the rigid body is in a release position in a landing gear according to a second embodiment. FIG. 13 is a schematic diagram showing a state in which the rigid body is in a release position in a first modified example of the second embodiment. FIG. 14 is a perspective view of a landing gear with a cargo bed.

[0011] Hereinafter, an embodiment will be described with reference to the drawings.

[0012] <First embodiment> Figure 1 is a schematic side view of a rotary-wing aircraft 1 according to the first embodiment. The rotary-wing aircraft 1 described in this embodiment is a single-rotor helicopter equipped with one main rotor 6. The rotary-wing aircraft 1 includes a fuselage 2 and landing gear 3 that supports the fuselage 2 on a landing surface. For convenience, the concept of directions in the following description is based on the fuselage 2 of the rotary-wing aircraft 1 when it has landed on a horizontal surface.

[0013] The fuselage 2 supports a prime mover 4, a transmission 5, a main rotor 6, and a tail rotor 7. For example, the prime mover 4 includes a turbine, a reciprocating engine, or an electric motor. The transmission 5 supports a main shaft 8 extending upward from the transmission 5. The main rotor 6 is attached to the upper end of the main shaft 8.

[0014] The main rotor 6 is disposed above the fuselage 2. The main rotor 6 is rotated by rotational power input from the prime mover 4 via the transmission 5 and the main shaft 8. The main rotor 6 rotates to generate lift that moves the rotary-wing aircraft 1 in the vertical direction and thrust that moves the rotary-wing aircraft 1 in a direction different from the vertical direction. In this embodiment, the main rotor 6 includes four rotor blades 6a. The tail rotor 7 is disposed rearward of the fuselage 2. Specifically, a tail boom 9 extends rearward from the fuselage 2, and the tail rotor 7 is disposed at the rear end of the tail boom 9. The tail rotor 7 rotates by rotational power input from the prime mover 4 via the transmission 5, a drive shaft, and the like. The tail rotor 7 generates lateral thrust to cancel out the counter torque generated in the fuselage 2 as a reaction to the rotation of the main rotor 6.

[0015] [Landing Gear] Figure 2 is a perspective view of the landing gear 3 of the rotorcraft 1 of Figure 1. The landing gear 3 includes a fixed body 3A and a support body 3B. The fixed body 3A is fixedly attached to the fuselage 2 of the rotorcraft 1. The fixed body 3A includes a mount body 11. The support body 3B includes at least one ground body 3C. The at least one ground body 3C includes a plurality of skids 12. In this embodiment, the number of skids 12 is two. The support body 3B includes, in addition to the at least one ground body 3C, a plurality of cross tubes 13 and a plurality of brackets 16. In this embodiment, the number of cross tubes 13 is two.

[0016] The mount body 11 is fixed to the fuselage 2 at the landing gear 3. In this embodiment, the mount body 11 includes an annular frame that is roughly rectangular in top view. The shape of the mount body 11 is not limited to an annular frame. The mount body 11 may include, for example, a plate-shaped frame. The mount body 11 may include, for example, a plurality of frames that extend in the left-right direction and are spaced apart in the front-to-rear direction. The mount body 11 may include, for example, a plurality of frames that extend in the front-to-rear direction and are spaced apart in the left-to-right direction.

[0017] The two skids 12 contact the landing surface when the rotorcraft 1 is not in flight. The non-flight state may also be referred to as a landing state. Each skid 12 extends in the fore-and-aft direction. The two skids 12 are spaced apart from each other in the left-and-right direction.

[0018] Each cross tube 13 extends in the left-right direction and is connected to two skids 12. The two cross tubes 13 are arranged at a distance from each other in the front-rear direction. One of the pair of skids 12 is connected to a first end of each cross tube 13 in the left-right direction, and the other of the pair of skids 12 is connected to a second end of each cross tube 13 in the left-right direction, which is different from the first end.

[0019] Each cross tube 13 has a generally arched shape curved such that the central portion in the left-right direction protrudes upward in a front view. More specifically, each cross tube 13 includes a pair of rising tube portions 13a and an intermediate tube portion 13b. Each cross tube 13 is disposed substantially parallel to a plane perpendicular to the front-to-rear direction. The pair of rising tube portions 13a rise obliquely upward from the pair of skids 12 toward the center of the cross tube 13 in the left-to-right direction. The intermediate tube portion 13b extends substantially linearly in the left-to-right direction and is connected to the upper ends of the rising tube portions 13a.

[0020] In this embodiment, the landing gear 3 has four brackets 16. The brackets 16 attach the cross tube to the mount body 11. The four brackets 16 are the connection points between the cross tube 13 and the mount body 11.

[0021] Two brackets 16 are disposed for each cross tube 13. Specifically, the two brackets 16 are disposed on the intermediate tube portion 13b with a gap between them in the left-right direction. The four brackets 16 face the mount body 11 in the up-down direction. At least one spring 21 and at least one rigid body 22 are disposed between the mount body 11 and each bracket 16 in the up-down direction.

[0022] Figure 3 is an enlarged side view of the vicinity of the spring 21 and rigid body 22 in the landing gear 3 of Figure 2. Figure 4 is an enlarged front view of the vicinity of the spring 21 and rigid body 22 in the landing gear 3 of Figure 2. Figures 3 and 4 show the configuration of the vicinity of one of the four brackets 16 as a representative, but the configurations of the vicinity of the other brackets 16 are also substantially the same as the configuration shown in Figures 3 and 4.

[0023] The bracket 16 holds the cross tube 13. A retaining hole 16a is formed in the bracket 16. The retaining hole 16a penetrates the bracket 16 in the left-right direction. The retaining hole 16a is located in the middle of the bracket 16 in the front-rear direction. The bracket 16 has a middle portion 16b in which the retaining hole 16a is formed, and end portions 16c extending in the front-rear direction from an upper portion of the middle portion 16b. The diameter of the retaining hole 16a is approximately the same as the diameter of the cross tube 13. The bracket 16 holds the cross tube 13 that is inserted through the retaining hole 16a. The shape of the bracket 16 and the method of fixing the bracket 16 to the cross tube 13 are not limited to those described above. For example, the bracket 16 does not need to have the retaining hole 16a for inserting the cross tube 13. For example, the bracket 16 may be fixed to the cross tube 13 with a fastener such as a bolt. For example, the bracket 16 may be composed of multiple members, and the cross tube 13 may be held by being sandwiched between the multiple members. The bracket 16 may be in the shape of a plate or a rectangular parallelepiped.

[0024] 3, the bracket 16 is connected to the mount body 11 via two springs 21. The two springs 21 overlap the bracket 16 and the mount body 11 in the up-down direction. The two springs 21 are spaced apart from each other in the front-rear direction.

[0025] The spring 21 includes a coil spring. A center line C1 of the spring 21 extends in the vertical direction. The upper end of the spring 21 is fixed to the mount body 11, and the lower end of the spring 21 is fixed to the bracket 16. Therefore, the spring 21 connects the mount body 11 and the bracket 16 while allowing the mount body 11 and the bracket 16 to move relative to each other in the vertical direction. When the mount body 11 and the bracket 16 move toward each other, the spring 21 contracts, and when the mount body 11 and the bracket 16 move away from each other, the spring 21 expands.

[0026] One rigid body 22 is arranged for one spring 21. Two rigid bodies 22 corresponding to the two springs 21 connected to the bracket 16 are arranged at a distance in the front-rear direction. Specifically, the rigid bodies 22 have a cylindrical shape that opens in the vertical direction and forms a hollow space. At least a portion of each spring 21 is arranged in the hollow space surrounded by each rigid body 22. In this embodiment, the rigid bodies 22 have a cylindrical shape. For example, the center line C1 of each spring 21 coincides with the center line C2 extending in the vertical direction of the rigid body 22. The center line C1 of each spring 21 does not have to coincide with the center line C2 extending in the vertical direction of the rigid body 22. The rigid body 22 may have a bottomed cylindrical shape, a square cylindrical shape, or the like. The rigid body 22 does not have to have a cylindrical shape.

[0027] Two springs 21 and two rigid bodies 22 are arranged for each bracket 16, so the landing gear 3 of this embodiment has eight springs 21 and eight rigid bodies 22 in total.

[0028] [Dynamic Vibration Absorber] When the rotary-wing aircraft 1 is in flight, various elements located on the opposite side of the fuselage 2 from the springs 21 are suspended and supported by the springs 21. As shown in FIG. 2 , the springs 21 constitute part of a dynamic vibration absorber D for reducing vibration of the fuselage 2 of the rotary-wing aircraft 1 when the rotary-wing aircraft 1 is in flight. More specifically, the dynamic vibration absorber D is configured as a so-called passive dynamic vibration absorber. The dynamic vibration absorber D includes the springs 21 and a first mass X1 that is located on the opposite side of the springs 21 from the fuselage 2, which is the object of vibration. In this embodiment, the first mass X1 is an element that is suspended and supported by the springs 21 during flight of the rotary-wing aircraft 1. The first mass X1 includes a support 3B. More specifically, the first mass X1 includes a plurality of skids 12, a plurality of cross tubes 13, and a plurality of brackets 16.

[0029] The dynamic vibration absorber D suppresses resonance phenomena in the fuselage 2, which is the object to be vibrated. The dominant frequency that occurs in the fuselage 2 when the rotorcraft 1 is in flight is set as the frequency at which vibrations are to be suppressed and is set as the target frequency of the dynamic vibration absorber D. Specifically, the spring 21 of the dynamic vibration absorber D is a spring with a spring constant that corresponds to the target frequency.

[0030] The method for determining the spring constant will be described in more detail. For example, it is known that helicopter vibrations tend to be dominated by frequency components that are integer multiples of the rotational speed of the main rotor, particularly integer multiples of the product of the rotational speed of the main rotor and the number of rotor blades. For example, if the number of rotor blades is four, the amplitude tends to be greatest at a frequency four times the rotational speed of the main rotor, and the amplitude tends to be second greatest at a frequency eight times the rotational speed of the main rotor. The frequency four times the rotational speed of the main rotor is also referred to as the fourth-order rotational component. The frequency eight times the rotational speed of the inner rotor is also referred to as the eighth-order rotational component. In this embodiment, the target frequency is set to a value that depends on the rated rotational speed of the main rotor 6 and the number of rotor blades 6a. The spring constant of each spring 21 is determined to suppress vibration at the set target frequency. More specifically, the spring constant is determined by the weight of the second mass X2 including the fuselage 2, the weight of the first mass X1, and the target frequency. The second mass X2 is located on the opposite side of the spring 21 from the first mass X1, and is an element connected to the upper side of the spring 21. In addition to the fuselage 2, the second mass X2 includes components such as the prime mover 4, transmission 5, main rotor 6, tail rotor 7, and tail boom 9 that move integrally with the fuselage 2 and move relative to the first mass X1 in flight.

[0031] Furthermore, in this embodiment, the dynamic vibration absorber D is configured as a so-called multi-stage dynamic vibration absorber that suppresses vibrations of multiple target frequencies. Specifically, two frequencies, a first target frequency and a second target frequency, are set as target frequencies of the dynamic vibration absorber D, and the multiple springs 21 include first springs 21 having a first spring constant and second springs 21 having a second spring constant different from the first spring constant. The first spring constant is set to suppress vibrations of the first target frequency, and the second spring constant is set to suppress vibrations of the second target frequency. In this embodiment, a fourth-order rotational component, which is a frequency four times the rotation speed of the main rotor 6, is set as the first target frequency, and an eighth-order rotational component, which is a frequency eight times the rotation speed of the main rotor 6, is set as the second target frequency.

[0032] For example, a first spring 21 having a first spring constant is arranged on one to three predetermined brackets 16 out of the four brackets 16, and a second spring 21 having a second spring constant is arranged on the remaining brackets 16.

[0033] [Rigid Body Movement Mechanism] The rigid body 22 moves relative to the mount body 11 depending on the state of the rotary-wing aircraft 1. When the rotary-wing aircraft 1 is not in a flight state, the rigid body 22 is located in the limiting position. The limiting position is a position where the rigid body 22 physically restricts the mount body 11 and the bracket 16 from approaching each other. When the rotary-wing aircraft 1 is in a flight state, the rigid body 22 is located in the release position. The release position is a position where the bracket 16 is allowed to approach the mount body 11 even closer than the position of the bracket 16 where the bracket 16 is closest to the mount body 11 when the rigid body 22 is located in the limiting position. The limiting position is a position where the relative movement of the fixed body 3A and the support body 3B is restricted at least in the vertical direction, and the release position is a position where the relative movement of the fixed body 3A and the support body 3B in the vertical direction is not restricted at all when the rotary-wing aircraft 1 is not in a flight state.

[0034] 5 and 6 are schematic diagrams showing the configuration of the spring 21, the rigid body 22, and the surrounding area in the first embodiment. Fig. 5 shows the rigid body 22 in the restricting position, and Fig. 6 shows the rigid body 22 in the releasing position. In Figs. 5 and 6, the rigid body 22, the mount body 11, and the bracket 16 are shown in cross section taken along the center line C1 of the spring 21.

[0035] The landing gear 3 further includes a plurality of actuators 23. The actuators 23 move the rigid bodies 22 between a restricting position and a releasing position. In this embodiment, one actuator 23 is arranged corresponding to one bracket 16. One actuator 23 moves two rigid bodies 22 arranged corresponding to one bracket 16. In Figures 5 and 6, for simplicity of illustration, only one rigid body 22 driven by the actuator 23 is shown.

[0036] In this embodiment, the actuator 23 is an electric rotary motor that rotates forward and backward. The actuator 23 includes an actuator body 23a and an output shaft 23b that protrudes from the actuator body 23a. The actuator body 23a is fixed to the mount body 11. The output shaft 23b of the actuator 23 extends downward from the actuator body 23a. A gear 23c is fixed to the output shaft 23b.

[0037] In this embodiment, the landing gear 3 further includes a linear motion conversion mechanism 30. The linear motion conversion mechanism 30 converts the rotational motion of the output shaft 23b of the actuator 23 into linear motion of the rigid body 22. The linear motion conversion mechanism 30 includes a gear 31 fixed to the outer circumferential surface of the rigid body 22, a female screw 32 located on the inner circumferential surface of the rigid body 22, and a male screw 33 disposed on the mount body 11 and engaging with the female screw 32.

[0038] Specifically, a gear 31 is fixed to the outer peripheral surface of the upper portion 22a of the rigid body 22. The gear 31 meshes with a gear 23c on the output shaft 23b. The rigid body 22 has a female thread 32 on the inner peripheral surface of the upper portion 22a. The lower portion of the mount body 11 has a cylindrical portion 11a that protrudes downward. The cylindrical portion 11a overlaps with the hollow space in the rigid body 22 when viewed from below. The diameter of the cylindrical portion 11a is substantially equal to the diameter of the inner peripheral surface of the rigid body 22. A male thread 33 is located on the outer peripheral surface of the cylindrical portion 11a. The female thread 32 located on the inner peripheral surface of the upper portion 22a of the rigid body 22 and the male thread 33 located on the outer peripheral surface of the cylindrical portion 11a of the mount body 11 engage with each other.

[0039] When the output shaft 23b of the actuator 23 rotates, a gear 23c that rotates together with the output shaft 23b engages with a gear 31 fixed to the rigid body 22, causing the rigid body 22 to rotate about the center line C2. Because the female thread 32 of the rigid body 22 engages with the male thread 33 of the mount body 11, the rigid body 22 moves up and down while rotating about the center line C2 in response to the rotation of the output shaft 23b. In other words, the rigid body 22 moves up and down while rotating, guided by the male thread 33 on the outer circumferential surface of the cylindrical portion 11a. By switching the rotation direction of the output shaft 23b of the actuator 23, the rigid body 22 moves up and down between the release position and the limit position.

[0040] The linear motion conversion mechanism 30 is not limited to the above configuration and may include, for example, a ball screw mechanism, a feed screw mechanism, a crank mechanism, an eccentric cam mechanism, or a rack and pinion.

[0041] 5 and 6, the mount body 11 is connected to the rigid body 22 whether the rigid body 22 is in the restricting position or the releasing position. When the rigid body 22 moves between the restricting position and the releasing position, the engagement between the female thread 32 and the male thread 33 is maintained.

[0042] [Engagement Structure] The rigid body 22 includes a first engagement structure 41, and the bracket 16 includes a second engagement structure 42 that can engage with the first engagement structure 41. When the rigid body 22 is in the limit position, the first engagement structure 41 engages with the second engagement structure 42. The rigid body 22 in the limit position connects the mount body 11 and the bracket 16 so that they cannot move relative to each other in the up and down direction.

[0043] In this embodiment, the first engagement structure 41 includes a female thread located on the inner circumferential surface of the lower portion of the rigid body 22. The bracket 16 has a cylindrical portion 16d that protrudes upward, and the second engagement structure 42 includes a male thread located on the outer circumferential surface of the cylindrical portion 16d. In the following description, the "first engagement structure 41" may be referred to as the "female thread 41," and the "second engagement structure 42" may be referred to as the "male thread 42."

[0044] The bracket 16 has a columnar portion 16d surrounded by a cylindrical groove 16e that opens upward. When the rigid body 22 is in the release position, the columnar portion 16d is located below the rigid body 22. The diameter of the columnar portion 16d is substantially equal to the diameter of the inner circumferential surface of the rigid body 22. When viewed from the top and bottom, the columnar portion 16d overlaps with the hollow space of the rigid body 22. The groove 16e has a size that allows the lower part of the rigid body 22 to fit in. The pitch of the female thread 41 and the male thread 42 is equal to the pitch of the female thread 32 and the female thread 32.

[0045] As the output shaft 23b of the actuator 23 rotates in a first direction around the center line C1 and moves downward from the release position, the lower end of the female thread 41 of the rigid body 22 reaches the upper end of the male thread 42 of the bracket 16. As the rigid body 22 further rotates in the first direction, the female thread 41 of the rigid body 22 and the male thread 42 of the bracket 16 begin to engage, and the lower part of the rigid body 22 enters the groove 16e and moves further downward. When the female thread 41 and the male thread 42 engage with each other and the rigid body 22 is positioned in the release position, the mount body 11 and the bracket 16 are connected to each other and are immovable relative to each other. As the output shaft 23b of the actuator 23 rotates in a second direction around the center line C1 and moves upward from the release position, the female thread 41 moves away from the male thread 42, and the mount body 11 and the bracket 16 are connected to each other and are movable relative to each other.

[0046] [Control System] Figure 7 is a block diagram showing a control system for moving the rigid body 22. The rotary-wing aircraft 1 includes a controller 50 that controls the actuator 23. The controller 50 may include one control unit or multiple control units. The multiple control units may be located remotely from one another. In terms of hardware, the controller 50 includes at least one CPU 51, at least one memory 52, an I / O interface, and the like. The at least one memory 52 includes, for example, a volatile memory and a non-volatile memory. The CPU 51, memory 52, and the like in the controller 50 are an example of a processing circuit configured to control the actuator 23.

[0047] In this embodiment, the controller 50 is fixed to the mount body 11. The controller 50 may also be fixed to a location other than the mount body 11, such as the body 2.

[0048] The controller 50 is electrically connected to a plurality of actuators 23. The CPU 51 of the controller 50 acquires state information indicating whether the rotorcraft 1 is in a non-flight state or a flight state. The CPU 51 controls the actuators 23 based on the state information. The state information includes information indicating whether the rotorcraft 1 has transitioned from one of the non-flight state and the flight state to the other state.

[0049] In this embodiment, at least one sensor 24 is electrically connected to the controller 50. The controller 50 receives information detected by the sensor 24 from the sensor 24, and the CPU 51 generates status information by determining the status of the rotary-wing aircraft 1 based on the received information.

[0050] The at least one sensor 24 detects, for example, at least one of a distance from the ground and an altitude. The at least one sensor 24 includes an ultrasonic sensor, a barometric pressure sensor, a GPS sensor, or any combination of these sensors. The at least one sensor 24 may be fixed to the landing gear 3. The at least one sensor 24 may be fixed to the fuselage 2. When the at least one sensor 24 is fixed to the landing gear 3, it is fixed to the mount body 11, for example.

[0051] The actuators 23, the controller 50 and the at least one sensor 24 are powered by a battery or a generator, which may be fixed to the landing gear 3, for example. The battery or generator may be fixed to the fuselage 2.

[0052] Figure 8 is a flowchart showing the flow of control by the controller 50 of Figure 7. When the rotorcraft 1 is not in flight, the rigid body 22 is maintained in the restricted position as shown in Figure 5. When the rigid body 22 is in the restricted position and the rotorcraft 1 is not in flight, the rigid body 22 supports at least a portion of the load of the fuselage 2, and therefore reduces the load applied to the spring 21. For example, when power is supplied to the controller 50 to start up, the controller 50 repeatedly executes the processing of the flowchart of Figure 8 until the supply of power is stopped.

[0053] In step S1, while the rigid body 22 is in the restricted position, the CPU 51 determines whether the rotary-wing aircraft 1 will transition from a non-flight state to a flight state. In other words, while the rigid body 22 is in the restricted position, the CPU 51 determines whether the rotary-wing aircraft 1 will take off.

[0054] If it is determined in step S1 that the rotary-wing aircraft 1 will transition from a non-flight state to a flight state or that the rotary-wing aircraft 1 will take off, then in step S2 the CPU 51 controls the actuator 23 to move the rigid body 22 from the restriction position to the release position. While the rotary-wing aircraft 1 is flying, the rigid body 22 is in the release position, causing the first mass body X1 to vibrate and reducing vibration of the fuselage 2. The timing at which it is determined that the rotary-wing aircraft 1 will take off is immediately after the skid 12 leaves the landing surface. The timing at which it is determined that the rotary-wing aircraft 1 will take off is not limited to this, and may be, for example, immediately before the skid 12 leaves the landing surface. When step S2 ends, the process proceeds to step S3.

[0055] In step S3, while the rigid body 22 is in the release position, the CPU 51 determines whether the rotorcraft 1 will transition from a flight state to a non-flight state. In other words, while the rigid body 22 is in the release position, the CPU 51 determines whether the rotorcraft 1 will land.

[0056] If it is determined in step S3 that the rotorcraft 1 will transition from a flight state to a non-flight state or that the rotorcraft 1 will land, the CPU 51 controls the actuator 23 to move the rigid body 22 from the release position to the restriction position, and then proceeds to step S1. The timing at which it is determined that the rotorcraft 1 will land is immediately before the skid 12 comes into contact with the landing surface. The timing at which it is determined that the rotorcraft 1 will land is not limited to this, and may be, for example, immediately after the skid 12 comes into contact with the landing surface.

[0057] According to this embodiment, vibrations of the rotary wing aircraft 1 during flight can be suppressed, and the degree of freedom in designing the springs 21 used to suppress the vibrations can be improved.

[0058] When the rigid body 22 is in the released position, the mount body 11 and the bracket 16 are allowed to approach each other. By positioning the rigid body 22 in the released position while the rotorcraft 1 is in flight, the skid 12 and the like can be vibrated relative to the mount body 11. In other words, the support body 3B can be used as the first mass body X1 of the dynamic vibration absorber D, and vibrations while the rotorcraft 1 is in flight can be suppressed.

[0059] For example, a conventional rotorcraft equipped with a dynamic vibration absorber that uses a skid as a mass body does not have an element corresponding to the rigid body 22 of this embodiment. When a conventional rotorcraft is not in flight, the load of the fuselage is supported by the spring for the dynamic vibration absorber. Therefore, in a conventional rotorcraft, the spring for the dynamic vibration absorber must have the strength to support the fuselage, which makes spring design difficult.

[0060] In this embodiment, when the rigid body 22 is in the limiting position, the rigid body 22 physically limits the mount body 11 and the bracket 16 from approaching each other. When the rigid body 22 is positioned in the limiting position while the rotorcraft 1 is not in flight, the rigid body 22 physically limits the mount body 11 from approaching the bracket 12, and supports the load of the fuselage 2. Therefore, the spring 21 used to suppress vibration does not need to be strong enough to support the fuselage, which improves the degree of freedom in designing the spring 21.

[0061] Furthermore, according to this embodiment, the rigid body 22 located in the limiting position not only restricts the mount body 11 and the bracket 16 from approaching each other, but also restricts them from moving away from each other. The rigid body 22 fixes the relative positions of the mount body 11 and the bracket 16, thereby increasing the rigidity of the landing gear 3. For example, by positioning the rigid body 22 in the limiting position, the position of the fuselage 2 relative to the landing gear 3 can be maintained at a predetermined position even when the rotorcraft 1 lands on uneven ground.

[0062] According to this embodiment, the landing gear 3 includes the actuator 23 that moves the rigid body 22, so that the actuator 23 can easily move the rigid body 22 between the restricting position and the releasing position.

[0063] According to this embodiment, the skid 12 and the cross tube 13 can be used as the first mass X1 of the dynamic vibration absorber D. Because not only the skid 12 but also the cross tube 13 can be used as the first mass X1, it is possible to reduce as much as possible the difference in weight between the first mass X1 and the second mass X2 of the dynamic vibration absorber D. By reducing the difference in weight between the first mass X1 and the second mass X2 of the dynamic vibration absorber D, it is possible to improve the vibration reduction effect on the fuselage 2 during flight of the rotorcraft 1.

[0064] According to this embodiment, the multiple springs 21 include a first spring 21 having a first spring constant and a second spring 21 having a second spring constant different from the first spring constant, so that the resonance phenomenon of the body 2 at multiple frequencies can be suppressed.

[0065] According to this embodiment, the rigid body 22 has a cylindrical shape, and at least a portion of the spring 21 is disposed in the hollow space of the rigid body 22, so that at least a portion of the spring 21 can be protected.

[0066] Modifications of the first embodiment will be described below with reference to Figures 9 to 16. In the first to fourth modifications of the first embodiment, components that are the same as or similar to those in the first embodiment are designated by the same reference numerals, and redundant descriptions may be omitted.

[0067] 9 and 10 are schematic diagrams showing the vicinity of the spring 21 and the rigid body 22 in a first modified example of the first embodiment. Fig. 9 shows the rigid body 22 in a restricted position, and Fig. 10 shows the rigid body 22 in a released position. In Figs. 9 and 10, the rigid body 22, the mount body 11, and the bracket 16 are shown in a cross section taken along the center line C1 of the spring 21.

[0068] The landing gear 3 of the first modified example has a linear motion conversion mechanism 30A instead of the linear motion conversion mechanism 30. The landing gear 3 of the first modified example includes, instead of the columnar portion 11a, a cylindrical body 61 that protrudes downward from the mount body 11 at the bottom of the mount body 11. The cylindrical body 61 has a male thread 33A on the outer periphery. The female thread 32 of the rigid body 22 engages with the male thread 33A of the cylindrical body 61. The linear motion conversion mechanism 30A has a male thread 33A of the cylindrical body 61 instead of the male thread 33. The cylindrical body 61 may be fixed to the mount body 11 by welding, for example, or may be connected to the mount body 11 by connecting the male thread 33A to the female thread of the mount body 11.

[0069] The cylindrical body 61 is separate from the mount body 11 and is fixed to the lower part of the mount body 11. The center line C3 of the cylindrical body 61 overlaps with the hollow space of the rigid body 22 when viewed from below. The diameter of the outer peripheral surface of the cylindrical body 61 is substantially equal to the diameter of the inner peripheral surface of the rigid body 22. The center line C2 of the rigid body 22 coincides with the center line C3 extending in the up-down direction of the cylindrical body 61. A male thread 33A is located on the outer peripheral surface of the cylindrical body 61.

[0070] The spring 21 is located radially inward of the cylindrical body 61 and the rigid body 22. The upper part of the spring 21 is disposed in the hollow space surrounded by the cylindrical body 61. For example, the center line C1 of the spring 21 coincides with the center line C3 of the cylindrical body 61 extending in the up-down direction.

[0071] The first modified example also provides the same effects as the first embodiment. In the first modified example, at least a portion of the spring 21 is disposed in the hollow space surrounded by the cylindrical body 61, so that at least a portion of the spring 21 can be protected by the cylindrical body 61. Because the mount body 11 and the cylindrical body 61 are separate bodies, it is easy to form the male thread 33A.

[0072] (Second Modification of First Embodiment) A second modification of the first embodiment will be described with reference to Figs. 11 to 13. Fig. 11 is a schematic diagram showing the vicinity of the spring 21 and the rigid body 71 in the second modification of the first embodiment. Fig. 12 is a perspective view of the lower part of the rigid body 71 in the second modification of the first embodiment. Fig. 13 is a cross-sectional view taken along the arrows XIII-XIII in Fig. 11.

[0073] In Fig. 11, the rigid body 71, the mount body 11, and the bracket 16 are shown in cross section taken along the center line C1 of the spring 21. The spring 21 is omitted in Fig. 13. In Figs. 11 and 13, the rigid body 71 is shown in the release position, and the rigid body 71 in the limit position is shown by a two-dot chain line.

[0074] In the second modified example, unlike the first embodiment, the rigid body 71 does not move in the vertical direction. In the second modified example, the rigid body 71 rotates around the center line C2 between the restricting position and the releasing position in response to rotation of the output shaft 23b of the actuator 23, without moving in the vertical direction.

[0075] Specifically, the rigid body 71 has a cylindrical shape that is open in the vertical direction. The rigid body 71 has a cylindrical shape. At least a portion of each spring 21 is disposed in a hollow space surrounded by the rigid body 71. For example, a center line C1 of the spring 21 coincides with a center line C2 of the rigid body 71 that extends in the vertical direction.

[0076] A gear 31 is fixed to the outer peripheral surface of the upper portion of the rigid body 71. The gear 31 meshes with a gear 23c on the output shaft 23b of the actuator 23. The diameter of the cylindrical portion 11a is substantially equal to the inner diameter of the inner peripheral surface 71a of the rigid body 71. The cylindrical portion 11a guides the rigid body 71 so that it rotates around the center line C2. For example, the rigid body 71 may have an annular groove extending circumferentially on the inner peripheral surface 71a, and the cylindrical portion 11a may have an annular protrusion protruding radially outward on the outer peripheral surface 11b. The rigid body 71 may be rotatably held on the mount body 11 by the annular protrusion fitted into the annular groove. For example, the rigid body 71 may have an annular protrusion protruding radially inward on the inner peripheral surface 71a, and the cylindrical portion 11a may have an annular groove extending circumferentially on the outer peripheral surface 11b.

[0077] When the output shaft 23b of the actuator 23 rotates, the gear 23c, which rotates together with the output shaft 23b, engages with the gear 31 fixed to the rigid body 71, causing the rigid body 71 to rotate about the center line C2. Unlike the first embodiment, the rigid body 71 does not have the female thread 32 and the mount body 11 does not have the male thread 33, so the rigid body 71 does not move in the vertical direction.

[0078] The rigid body 71 includes a first engagement structure 71b. The bracket 16 includes a second engagement structure 84 that is engageable with the first engagement structure 71b. The first engagement structure 71b includes an engagement protrusion. The second engagement structure 84 is a portion of the bracket 16 that forms an engagement groove into which the engagement protrusion fits. In the following description, the "first engagement structure 71b" may be referred to as the "engagement protrusion 71b," and the "second engagement structure 84" may also be referred to as the "engagement groove 84."

[0079] As shown in Figure 12, the rigid body 71 has a pair of engagement protrusions 71b on the outer peripheral surface of the lower part of the cylindrical portion 71a. The pair of engagement protrusions 71b are positioned rotationally symmetrically with respect to the center line C2 when viewed from the top-bottom direction. The pair of engagement protrusions 71b protrude radially outward from the cylindrical portion 71a of the rigid body 71. The pair of engagement protrusions 71b protrude in directions away from each other.

[0080] The bracket 16 has a hole 81 that is located below the rigid body 71 and opens upward. As shown in Figure 11, the lower end of the spring 21 is fixed to a bottom surface 82 of the inner circumferential surface that defines the hole 81 in the bracket 16.

[0081] 13, the hole 81 has a substantially rectangular shape when viewed from above. The hole 81 has a shape and size that allows the lower part of the rigid body 71 to fit into the hole 81 when the rigid body 71 is in a predetermined position.

[0082] When the protruding direction of the engaging protrusion 71b on the rigid body 71 coincides with the longitudinal direction of the opening 81a of the bracket 16 that defines the hole 81, the lower part of the rigid body 71 can pass through the opening 81a of the hole 81, and when the protruding direction of the engaging protrusion 71b on the rigid body 71 is perpendicular to the longitudinal direction of the opening 81a of the hole 81, the lower part of the rigid body 71 cannot pass through the opening 81a of the hole 81.

[0083] The side surfaces 83 of the inner peripheral surface of the bracket 16 that define the hole 81 define a pair of engagement grooves 84 with which the pair of engagement protrusions 71b can respectively engage. Specifically, the pair of side surfaces 83 extending in the long side direction of the opening 81a each define an engagement groove 84. In FIG. 13 , the engagement grooves 84 are indicated by dashed lines. When the rigid body 71 is in the released position, the protruding direction of the engagement protrusions 71b on the rigid body 71 coincides with the longitudinal direction of the opening 81a. When the rigid body 71 is in the released position, the engagement protrusions 71b are not engaged with the bracket 16, and the lower end of the rigid body 71 is spaced apart from the bottom surface 82 in the up-down direction. This allows the bracket 16 to vibrate in the up-down direction relative to the rigid body 71 and the mount body 11 that supports the rigid body 71. When the rigid body 71 is positioned in the release position while the rotary-wing aircraft 1 is in flight, the skid 12 can move relative to the mount body 11 in the vertical direction, so that the support body 3B can be used as the first mass body X1 of the dynamic vibration absorber D, thereby suppressing vibrations while the rotary-wing aircraft 1 is in flight.

[0084] When the rigid body 71 in the release position is rotated around the center line C2, the rigid body 71 moves to a limiting position where the engagement protrusion 71b fits into the engagement groove 84. This prevents the bracket 16 from moving in the vertical direction relative to the rigid body 71. By positioning the rigid body 71 in the limiting position when the rotorcraft 1 is not in flight, the rigid body 71 can support the load of the fuselage 2.

[0085] The second modified example also provides the same effects as those of the first embodiment. Furthermore, in the second modified example, the rigid body 71 is not moved along the center line C2, so that the configuration for moving the rigid body 71 between the restricting position and the releasing position can be simplified.

[0086] Third Modification of First Embodiment FIG. 14 is a schematic enlarged view showing the vicinity of a spring 91 and a rigid body 92 in a third modification of the first embodiment.

[0087] The landing gear 3 of the third modified example includes an actuator 93. The actuator 93 moves the rigid body 92 between a restricting position and a releasing position. The actuator 93 includes a linear actuator that moves the rigid body 92 linearly. The actuator 93 includes an actuator main body 93a and an output shaft 93b protruding from the actuator main body 93a. The actuator main body 93a is fixed to the mount body 11. The output shaft 93b is supported by the actuator main body 93a so as to be reciprocable in the extension direction of the output shaft 93b. The output shaft 93b extends downward from the actuator main body 93a, and the rigid body 92 is fixed to the lower end of the output shaft 93b. The rigid body 92 is cylindrical, but is not limited to this. The linear actuator may be electric, hydraulic, or pneumatic. The rigid body 92 may be formed integrally with the output shaft 93b.

[0088] In the third modified example, the output shaft 93b and the rigid body 92 are located radially inward of the spring 91. The output shaft 93b and the rigid body 92 are located closer to the center line C1 than the spring 91. The output shaft 93b overlaps with the center line C1 of the spring 91 and extends along the center line C1. The rigid body 92 moves up and down on the center line C1 of the spring 91.

[0089] In Figure 14, the rigid body 92 in the release position is indicated by a solid line, and the rigid body 92 in the limit position is indicated by a two-dot chain line. By driving the actuator 93, the rigid body 92 moves up and down between the release position and the limit position. As indicated by the solid line in Figure 14, when the rigid body 92 is in the release position, the rigid body 92 is not in contact with the bracket 16, and therefore the bracket 16 is allowed to move in a direction toward the mount body 11.

[0090] When the actuator 93 is driven to move the rigid body 92 to the limiting position, the rigid body 92 abuts against the upper surface of the bracket 16, as shown by the two-dot chain line in Figure 14, thereby restricting the bracket 16 and the mount body 11 from approaching each other.

[0091] The third modified example also provides the same effects as those of the first embodiment. Furthermore, the third modified example makes it possible to effectively utilize the space radially inside the spring 91.

[0092] The landing gear 3 of this third modified example does not have the first engagement structure 41 and the second engagement structure 42 described in the first embodiment for connecting the mount body 11 and the bracket 16 so that they cannot move relative to each other. Therefore, when the rigid body 92 is in the limiting position, the rigid body 92 restricts the mount body 11 and the bracket 16 from moving toward each other, but does not restrict the mount body 11 and the bracket 16 from moving away from each other. This third modified example may also have configurations corresponding to the first engagement structure and the second engagement structure for restricting the mount body 11 and the bracket 16 from moving away from each other.

[0093] (Fourth Modification of First Embodiment) Fig. 15 is a schematic diagram showing an enlarged view of the vicinity of the spring 101 and the rigid body 102 in a fourth modification of the first embodiment, and showing a state in which the rigid body 102 is in the release position. Fig. 16 is a schematic diagram showing an enlarged view of the vicinity of the spring 101 and the rigid body 102 in the fourth modification of the first embodiment, and showing a state in which the rigid body 102 is in the restricting position.

[0094] The landing gear 3 of the fourth modified example does not include an actuator that moves the rigid body 102 between the restricted position and the released position. The rigid body 102 moves between the restricted position and the released position due to the gravity of various elements of the rotorcraft 1.

[0095] The rigid body 102 has a cylindrical shape that is open in the vertical direction. The upper end of the rigid body 102 is fixed to the mount body 11. At least a part of the spring 101 is located in the hollow space surrounded by the rigid body 102.

[0096] The cylindrical body 103 is disposed radially outward from the rigid body 102. The lower end of the cylindrical body 103 is fixed to the bracket 16. The cylindrical body 103, together with the rigid body 102, defines an accommodation space for accommodating the spring 101. The cylindrical body 103 covers the lower end of the rigid body 102 from the side even when the rigid body 102 is in the release position, and protects the spring 101 by covering the spring 101 from the side together with the rigid body 102.

[0097] When the rotorcraft 1 is in flight, gravity acting on the first mass X1 suspended from the spring 101 acts on the spring 101 in a direction that extends the spring 101. Therefore, the spring 101 is extended by the weight of the multiple skids 12, the multiple cross tubes 13, and the multiple brackets 16. As the spring 101 extends, the rigid body 102 is positioned in the release position, as shown in Fig. 15. The release position is a position where the rigid body 102 is spaced apart from the bracket 16 in the vertical direction. As the spring 101 extends, the first mass X1 suspended from the spring 101 vibrates during flight of the rotorcraft 1, and resonance of the fuselage 2 is suppressed.

[0098] When the rotorcraft 1 is not in flight, gravity acting on the mount 11, the fuselage 2, and other components located above the spring 101 acts on the spring 101 in a direction that compresses the spring 101. Therefore, the weight of the mount 11 and the fuselage 2 compresses the spring 101. As the spring 101 compresses, the rigid body 102 is positioned in contact with the bracket 16, as shown in Fig. 16. The position where the rigid body 102 contacts the bracket 16 is, in other words, the limit position. When the rigid body 102 contacts the bracket 16, the rigid body 102 supports at least a portion of the load of the fuselage 2, and therefore the rigid body 102 suppresses the load applied to the spring 101.

[0099] The fourth modified example also provides the same effects as those of the first embodiment. Furthermore, the fourth modified example does not include an actuator that moves the rigid body 102 between the restricting position and the releasing position, and therefore the configuration of the landing gear 3 can be simplified.

[0100] In the fourth modified example, the rigid body 102 may be fixed to the bracket 16, and the cylindrical body 103 may be fixed to the mount body 11. Also, a portion of the cylindrical body 103 may be disposed on the inner circumferential side of the rigid body 102. The cylindrical body 103 may be made of an elastic material such as rubber.

[0101] Second Embodiment A landing gear 110 according to a second embodiment and a rotary-wing aircraft including the same will be described with reference to Figure 17. The configuration of the rotary-wing aircraft of the second embodiment is the same as that of the first embodiment, except for the connection point between the cross tube 122 and the mount body 11. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and duplicated descriptions may be omitted. The connection point between the cross tube 122 and the mount body 11 is, in other words, a location near the bracket 121.

[0102] In the second embodiment and a first modified example of the second embodiment described below, the landing gear 110 has a fixed body 3C that includes a bracket 121 instead of the bracket 16. In the second embodiment and a first modified example of the second embodiment described below, the bracket 121 is included in the fixed body 3C, not the support body 3D. That is, the fixed body 3C that is fixedly attached to the fuselage 2 of the rotorcraft 1 includes the bracket 121 in addition to the mount body 11. The support body 3D includes a plurality of cross tubes 122 instead of the plurality of cross tubes 13. That is, the support body 3D includes a plurality of skids 12, which are the ground-contacting body 3C, and a plurality of cross tubes 122.

[0103] FIG. 17 is an enlarged schematic diagram showing the vicinity of the spring 111 and the rigid body 112 in the second embodiment, with the rigid body 112 in the released position.

[0104] The bracket 121 is fixed to the mount body 11 with fasteners such as bolts. In this embodiment, the bracket 121 has a through hole 121a through which the cross tube 122 passes and an inner circumferential surface 121b that defines the through hole 121a. The diameter of the through hole 121a is larger than the diameter of the cross tube 122. A spring 111 is disposed in the gap space between the inner circumferential surface 121b of the bracket 121 and the outer circumferential surface 122a of the cross tube 122. The spring 111 constitutes part of a dynamic vibration absorber.

[0105] The springs 111 are located below the cross tubes 122. The springs 111 include coil springs. A center line C4 of each spring 111 extends in the vertical direction. The upper end of each spring 111 is connected to the outer circumferential surface 122a of the cross tube 122, and the lower end of each spring 111 is connected to the inner circumferential surface 121b of the bracket 121.

[0106] The landing gear 110 of this embodiment includes an actuator 113. The actuator 113 moves the rigid body 112 between a restricted position and a released position. The actuator 113 includes an actuator body 113a and an output shaft 113b protruding from the actuator body 113a. The actuator 113 includes a linear actuator that linearly moves the rigid body 112. The output shaft 113b is supported by the actuator body 113a so as to be reciprocatable in the extension direction of the output shaft 113b. The linear actuator may be of an electric, hydraulic, or pneumatic type.

[0107] The actuator body 113a is fixed to the cross tube 122. Specifically, the actuator body 113a is fixed to the cross tube 122 while being disposed in a space radially inward of the cross tube 122. The output shaft 113b extends upward from the actuator body 113a. An opening 122b is formed at the top of the cross tube 122, and the output shaft 113b protrudes radially outward from the cross tube 122 through the opening 122b. A rigid body 112 is fixed to the upper end of the output shaft 113b. The rigid body 112 has a rectangular parallelepiped shape, but the shape of the rigid body 112 is not limited to this.

[0108] In this embodiment, the output shaft 113b extends on the center line C4 of the spring 111, and the rigid body 112 moves up and down on the center line C4. The extension direction of the output shaft 113b and the extension direction of the center line C4 of the spring 111 do not have to coincide. For example, the center line extending in the extension direction of the output shaft 113b may be parallel to the center line C4 of the spring 111 and offset in the left-right direction from the center line C4 of the spring 111.

[0109] In Figure 17, the rigid body 112 in the released position is shown by a solid line, and the rigid body 112 in the restricted position is shown by a two-dot chain line. By driving the actuator 113, the rigid body 112 moves up and down between the released position and the restricted position. As shown by the solid line in Figure 17, when the rigid body 112 is in the released position, the rigid body 112 does not abut against the inner circumferential surface 121b of the bracket 121. When the rigid body 112 is in the released position, the cross tube 122 and the mount body 11 are allowed to approach each other.

[0110] When the actuator 113 is driven to move the rigid body 112 from the release position to the restricting position, the rigid body 112 comes into contact with the inner peripheral surface 121b of the bracket 121, as shown by the two-dot chain line in Figure 17. When the rigid body 112 is in the restricting position, the mount body 11 and the cross tube 122 are restricted from approaching each other.

[0111] This embodiment also provides the same effects as those of Embodiment 1. Furthermore, in this embodiment, the actuator 113 is disposed in the through-hole 121 a of the bracket 121 , so that the actuator 113 can be protected by the bracket 121 .

[0112] In this embodiment, the actuator 113 may be engaged with the bracket 121 in a non-flight state so as to fix the relative position between the bracket 121 and the cross tube 122. In other words, the landing gear 110 of this embodiment may also be provided with a configuration corresponding to the first engagement structure 41 and the second engagement structure 42 described in the first embodiment for connecting the mount body 11 and the bracket 16 so as to prevent relative movement between them.

[0113] 18 is a schematic diagram illustrating an enlarged view of the spring 111 and the rigid body 112 in the vicinity thereof in a first modification of the second embodiment, showing the rigid body 112 in a released position. The landing gear 110 of this first modification further includes a spring 131 that oscillates in the horizontal direction in addition to the various elements of the second embodiment.

[0114] A pair of springs 131 is disposed for each bracket 121. The pair of springs 131 are located in the gap between the inner peripheral surface 121b of the bracket 121 and the outer peripheral surface 122a of the cross tube 122. One of the pair of springs 131 is located in front of the cross tube 122, and the other of the pair of springs 131 is located behind the cross tube 122. Each spring 131 includes a coil spring. A center line C5 of each spring 131 extends in the front-to-rear direction. One end of the spring 131 is connected to the outer peripheral surface 122a of the cross tube 122, and the other end of the spring 131 is connected to the inner peripheral surface 121b of the bracket 121.

[0115] The landing gear 110 of the first modified example can suppress vibrations in directions other than the up-and-down direction in the fuselage 2 of the rotorcraft 1. The landing gear 110 can suppress ground resonance, for example, when the rotorcraft 1 is not in flight.

[0116] Other Embodiments The present disclosure is not limited to the above-described embodiments and modifications, and the configurations of the above-described embodiments and modifications may be changed, added, or deleted.

[0117] For example, in the above first and second embodiments and their modified examples, a single-rotor helicopter having one main rotor has been described as the rotary-wing aircraft, but the rotary-wing aircraft is not limited to this. For example, the rotary-wing aircraft may be a twin-rotor helicopter having two main rotors, or a multi-rotor helicopter having three or more main rotors. Furthermore, the present disclosure is also applicable to rotary-wing aircraft other than helicopters. For example, the rotary-wing aircraft may be a manned rotary-wing aircraft or an unmanned rotary-wing aircraft such as a drone.

[0118] The configuration of the landing gear is not limited to the configurations described in the above first and second embodiments and their modifications.

[0119] For example, the positions of the springs for the dynamic vibration absorbers are not limited to the positions described in the first and second embodiments and their modifications.

[0120] For example, in the first embodiment and its modified examples, the spring 21 for the dynamic vibration absorber is located at the connection point between the mount body 11 and the bracket 16, but the spring for the dynamic vibration absorber may be located between the skid and the cross tube. The spring for the dynamic vibration absorber may be located in the middle part of the rising tube section 13a. In this case, each rising tube section 13a may include two tubes, an upper tube and a lower tube, which are separated from each other in the vertical direction, and the spring may be disposed between the upper tube and the lower tube.

[0121] For example, the landing gear may not have a cross tube. For example, the landing gear may not have a bracket. For example, instead of a cross tube, the landing gear may have a plurality of support legs extending linearly upward from the skid. In this case, the mount may be connected to the upper ends of the support legs, or the fuselage may be directly connected to the upper ends of the support legs. If the landing gear has support legs, the springs for the dynamic vibration absorbers may be located between the upper ends of the support legs and the fuselage, between the lower ends of the support legs and the skid, or in the middle of the support legs.

[0122] In the above embodiment and modified examples, skids are described as ground contacting bodies that come into contact with the landing surface when the rotorcraft is not in flight, but the ground contacting bodies do not have to include skids. For example, the ground contacting bodies may include running wheels instead of skids.

[0123] The elements included in the fixed body and the elements included in the support body may vary depending on the configuration of the landing gear or the position of the springs for the dynamic vibration absorbers. Elements on the same side of the spring as the ground body and that vibrate together with the ground body when the rotorcraft is in flight are included in the support body. Elements on the opposite side of the spring from the ground body and that vibrate together with the fuselage when the rotorcraft is in flight are included in the fixed body.

[0124] As shown in FIG. 19 , the landing gear may include a platform 14 on which cargo B is placed. For example, the platform 14 is disposed between a pair of skids 12. The platform 14 is suspended and supported by the two cross tubes 13 via a plurality of support rods 15 connected to the two cross tubes 13. In this case, the first mass X1, which is a component of the dynamic vibration absorber D, includes the platform 14, the support rods 15, and the cargo B in addition to the plurality of skids 12, the plurality of cross tubes 13, and the plurality of brackets 16. This increases the weight of the first mass X1, thereby improving the vibration suppression effect. The spring constant of the spring, which is a component of the dynamic vibration absorber D, may be set taking into account the weights of the platform 14, the support rods 15, and the cargo B.

[0125] The fixed body may be configured to be fixed to the fuselage. For example, the fixed body may be detachably fixed to the fuselage, or may be non-detachably fixed to the fuselage. The fixed body may be a part of the fuselage. The fixed body fixed to the fuselage may also include a part of the fuselage. The landing gear does not have to include the mount described in the above embodiment.

[0126] For example, the surface with which the grounding body comes into contact when the rotorcraft is not in flight, i.e., the surface on which the rotorcraft is placed, does not have to be the ground, and includes the top surface of a platform, the deck of a ship, the roof of a building, and the surface of a takeoff and landing site installed on a vehicle. Therefore, in this specification, landing surface refers to any surface on which a rotorcraft is placed when not in flight.

[0127] The configuration of the dynamic vibration absorber can be changed as appropriate. For example, the dynamic vibration absorber may include a damper in addition to a spring and a mass. The dynamic vibration absorber does not have to be a passive dynamic vibration absorber. The present disclosure is also applicable to a landing gear equipped with an active dynamic vibration absorber that includes an actuator that actively changes the spring constant of a spring to reduce vibration of a rotorcraft fuselage.

[0128] The number, shape, orientation, and position of the springs for the dynamic vibration absorbers included in the rotary-wing aircraft relative to the elements of the landing gear are not limited to those in the above embodiment. The springs for the dynamic vibration absorbers do not have to be coil springs, and may be leaf springs or other types of springs.

[0129] The number, shape, orientation, and position of the rigid bodies of the rotorcraft relative to each element of the landing gear are not limited to those in the above embodiment.

[0130] The rigid body may be supported by at least one of the fixed body and the support body. For example, in the first embodiment, when the rigid body is in the released position, the rigid body is connected to the mount body, which is part of the fixed body, and is not connected to the bracket, which is part of the support body. However, when the rigid body is in the released position, the rigid body may not be connected to the mount body, which is part of the fixed body, but may be connected to the bracket, which is part of the support body.

[0131] Although one rigid body 22 is provided for one spring 21 for the dynamic vibration absorber, the number of springs and rigid bodies for the dynamic vibration absorber may be different. For example, in the first embodiment and its modified examples, one rigid body may be provided for each bracket. The landing gear may include only one rigid body directly below the fuselage. The rigid body may be located at a position completely different from the spring, for example, in the center of the intermediate tube portion 13b in the left-right direction.

[0132] In the first embodiment, the two springs 21 are spaced apart from each other in the front-rear direction, but the arrangement of the springs is not limited to this. For example, the two springs 21 may be spaced apart in a predetermined direction in a plane perpendicular to the up-down direction, rather than in the front-rear direction.

[0133] The shape of the rigid body can be changed as appropriate. For example, in the modified example shown in FIG. 14 , the rigid body may have a cylindrical body with at least a portion of the spring 91 disposed radially inward. For example, the rigid body may be a cylindrical body having a diameter larger than that of the spring 91, and a linear actuator or linear motion conversion mechanism that moves the cylindrical body in the vertical direction may be disposed in the mount body 11 or the bracket 16. For example, in the modified example shown in FIG. 11 , the rigid body does not have to be a cylindrical body, and may be a solid material disposed radially inward of the spring 21.

[0134] The actuator for moving the rigid body may be of an electric, hydraulic or pneumatic type.

[0135] The number of actuators can be changed as appropriate. For example, in the first embodiment and its modified examples, the number of actuators 23 is the same as the number of brackets 16. However, the number of actuators 23 may be the same as the number of rigid bodies of the landing gear, or one actuator may drive one rigid body. One actuator may also drive three or more rigid bodies.

[0136] The location of the actuator can be changed as appropriate. In the above-described embodiment, the actuator body is fixed to the landing gear, but it may also be fixed to the fuselage. For example, in the first embodiment, the actuator body may be fixed to the bracket or the cross tube. For example, in the second embodiment, the actuator body may be fixed to the fixed body side instead of the support side. For example, in the second embodiment, the actuator body may be fixed to the bracket or the mount body side instead of the cross tube support side. In the above-described first embodiment, the gear 23c of the output shaft 23b of the actuator 23 is arranged to mesh with the gear 31 on the outer peripheral surface of the upper part 22a of the rigid body 22, but the gear of the actuator output shaft may also be arranged radially inward of the cylindrical rigid body.

[0137] The landing gear does not need to include an actuator for moving the rigid body. For example, even in the configuration of the second embodiment, instead of moving the rigid body with an actuator, the rigid body may be moved between a restricted position and an unlocked position relative to at least one of the fixed body and the support by the gravity of various elements of the rotary-wing aircraft, as illustrated in Figures 15 and 16. Generally speaking, when the rotary-wing aircraft is flying, the rigid body may be fixed to a first element of the fixed body and the support and positioned at a position spaced apart in the vertical direction from a second element of the fixed body and the support. When the rotary-wing aircraft lands, the spring compresses due to the weight of the fuselage, causing the rigid body to contact the second element. In this way, the spring constant, the vertical dimension of the spring, or the vertical dimension of the rigid body may be adjusted so that when the rotary-wing aircraft is flying, the rigid body and the second element are spaced apart to allow the support to vibrate, and when the rotary-wing aircraft is not flying, the rigid body abuts against the second element so that the support supports the weight of the fuselage.

[0138] For example, instead of including an actuator for moving the rigid body, the rotary-wing aircraft may include a displacement mechanism configured to displace the rigid body by, for example, manual power of a user. In this case, a lever that accepts user operation may be disposed on the fuselage of the rotary-wing aircraft, and the displacement mechanism may be a mechanism that displaces the rigid body between a release position and a limit position by operating the lever.

[0139] The method of movement of the rigid body is not particularly limited. The rigid body may move in an up-down direction or may move rotationally. The rigid body may move horizontally. The horizontal direction includes, for example, a direction perpendicular to the up-down direction, such as a front-back direction or a left-right direction. For example, when the support body and the fixed body have portions that face each other in the horizontal direction, the rigid body may be moved horizontally from the fixed body toward the support body to engage with the support body, thereby restricting the relative movement of the support body and the fixed body in the up-down direction.

[0140] The configurations of the first and second engagement structures are not limited to those described in the above embodiment. For example, one of the first and second engagement structures may include a female thread, and the other may include a male thread. For example, one of the first and second engagement structures may include a protrusion, and the other may include an engagement groove or hole into which the protrusion fits. The landing gear does not have to include the first and second engagement structures.

[0141] The location of the processing circuit that controls the actuator is not particularly limited, and the processing circuit does not have to be located on the mount body, but may be located on the fuselage.

[0142] The method of determining whether to transition from one of the non-flight state and the flight state to the other is not limited to the method described in the above embodiment. For example, whether to transition from one of the non-flight state and the flight state to the other may be determined using detection information from an altitude sensor that detects the altitude of the rotorcraft 1. For example, the altitude sensor may include a barometric pressure sensor or a GPS sensor. Whether to transition from one of the non-flight state and the flight state to the other may be determined using detection information from a distance sensor that detects the distance from the landing surface, i.e., the altitude above ground. For example, the distance sensor may include an ultrasonic sensor, LiDAR, radar, or the like. For example, whether to transition from one of the non-flight state and the flight state to the other may be determined using detection information from a load sensor that detects whether the landing gear 3 is in a state supporting the load of the fuselage 2. Whether to transition from one of the non-flight state and the flight state to the other may be determined using detection information from a contact sensor that detects whether the grounding body has touched down on the landing surface. Whether to transition from one of the non-flight state and the flight state to the other may also be determined using information related to the blade pitch angle.

[0143] The CPU 51 may receive status information from outside the controller 50, without determining whether the rotorcraft 1 is in a non-flight state or a flight state and generating status information. For example, the controller 50 may receive status information from another controller installed in the fuselage 2.

[0144] In the above embodiment, the spring 131 is arranged to connect the fixed body and the support body in the front-rear direction, but the arrangement of the spring 131 is not limited to this. For example, the spring 131 may be arranged to connect the fixed body and the support body in the left-right direction.

[0145] In the above embodiment, the dynamic vibration absorber was configured as a so-called multi-stage dynamic vibration absorber that suppresses vibrations of multiple target frequencies, but the dynamic vibration absorber may also be configured to suppress vibrations of one target frequency.

[0146] The landing gear may not include a spring that vibrates in the vertical direction as a part of the dynamic vibration absorber. The landing gear may include only a spring that vibrates in a direction other than the vertical direction as a part of the dynamic vibration absorber. For example, the spring that functions as a part of the dynamic vibration absorber in the landing gear may include only a spring that vibrates in the horizontal direction.

[0147] In the above embodiment, the first spring and the second spring included in the multi-stage dynamic vibration absorber were separate bodies, but instead of the first spring and the second spring, a two-stage spring in which the first spring and the second spring are integrated may be used.

[0148] A part of the configuration of one of the first and second embodiments and their modified examples may be applied to another configuration.

[0149] As described above, the above-described embodiments are described as examples of the technology disclosed in this application. However, the technology of the present disclosure is not limited thereto and can be applied to embodiments in which modifications, substitutions, additions, or omissions are appropriately made to the above-described embodiments. The components described in the above-described embodiments can also be combined to create new embodiments. For example, some configurations or methods in one embodiment may be applied to another embodiment, and some configurations in an embodiment may be separated and arbitrarily extracted from other configurations in that embodiment. The components described in the accompanying drawings and detailed description include not only components essential for solving the problem, but also components that are not essential for solving the problem, and are used to illustrate the technology. Two blocks shown in a sequential order in a flowchart may be executed simultaneously or in reverse order, depending on the circumstances.

[0150] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, special-purpose processors, integrated circuits, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. Processors are considered processing circuits or circuits because they include transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0151] Each of the following aspects is a disclosure of a preferred embodiment.

[0152] [Aspect 1] A landing gear for a rotary-wing aircraft, comprising: a fixed body fixed to a fuselage of the rotary-wing aircraft; a support including at least one ground-contacting body that comes into contact with a landing surface when the rotary-wing aircraft is not in a flight state; at least one spring that connects the fixed body and the support so that the fixed body and the support can move relative to each other, and that reduces vibration of the fuselage of the rotary-wing aircraft together with the support when the rotary-wing aircraft is in a flight state; and a rigid body that moves relative to at least one of the fixed body and the support between a restricting position that restricts the fixed body and the support from approaching each other and a releasing position that releases the restriction on the fixed body and the support from approaching each other.

[0153] According to the landing gear configuration of aspect 1, it is possible to provide a landing gear for a rotary-wing aircraft that can suppress vibrations during flight of the rotary-wing aircraft and improve the design freedom of the springs used to suppress vibrations, and a rotary-wing aircraft equipped with the same.

[0154] When the rigid body is in the release position, the fixed body and the support body are allowed to approach each other. Therefore, by positioning the rigid body in the release position while the rotorcraft is in flight, the support body can be vibrated relative to the fixed body. In other words, the support body can be used as a mass body of the dynamic vibration absorber, and vibrations while the rotorcraft is in flight can be suppressed.

[0155] When the rigid body is in the limiting position, the fixed body and the support are restricted from approaching each other. Therefore, by positioning the rigid body in the limiting position when the rotorcraft is not in flight, the load of the fuselage is supported by the rigid body that physically restricts the fixed body from approaching the support. Therefore, the spring used to suppress vibration does not need to have such high strength, and the degree of freedom in spring design can be improved.

[0156] [Aspect 2] A landing gear for a rotary-wing aircraft as described in Aspect 1, wherein the rigid body includes a first engagement structure; one of the fixed body and the support body supports the rigid body; the other of the fixed body and the support body includes a second engagement structure engageable with the first engagement structure; and the limiting position is a position where the first engagement structure and the second engagement structure engage with each other so as to limit the fixed body and the support body from moving away from each other.

[0157] According to the landing gear configuration of Aspect 2, the rigid body located in the limiting position not only limits the fixed body and the support body from moving toward each other, but also limits their moving away from each other. Since the relative movement between the fixed body and the support body is limited, the rigidity of the entire rotorcraft can be increased.

[0158] [Aspect 3] The landing gear for a rotary wing aircraft according to aspect 1 or 2, further comprising an actuator that moves the rigid body between the restricting position and the releasing position.

[0159] According to the landing gear configuration of aspect 3, the rigid body can be easily moved between the release position and the restriction position.

[0160] Aspect 4. The landing gear for a rotary-wing aircraft according to Aspect 3, further comprising a processing circuit configured to control the actuator, wherein the rigid body is maintained in the restricted position when the rotary-wing aircraft is in the non-flying state, and the processing circuit is configured to: control the actuator to move the rigid body from the restricted position to the released position when the rotary-wing aircraft transitions from the non-flying state to the flying state; and control the actuator to move the rigid body from the released position to the restricted position when the rotary-wing aircraft transitions from the flying state to the non-flying state.

[0161] According to the landing gear configuration of aspect 4, the rigid body can be positioned in the release position when the rotorcraft takes off, and the rigid body can be positioned in the restricted position when the rotorcraft lands.

[0162] [Aspect 5] The landing gear for a rotary-wing aircraft according to any one of Aspects 1 to 4, wherein the at least one ground-contacting body includes a pair of skids spaced apart from each other in the left-right direction, and the support body further includes at least one cross tube connecting the pair of skids.

[0163] According to the landing gear configuration of aspect 5, the pair of skids and the cross tube can be used as the mass body of the dynamic vibration absorber.

[0164] [Aspect 6] The landing gear for a rotary wing aircraft described in any one of Aspects 1 to 5, wherein the at least one spring includes: a first spring connected to the fixed body and the support so that the support can vibrate in an up-down direction relative to the fixed body, the first spring having a first spring constant; and a second spring connected to the fixed body and the support so that the support can vibrate in the up-down direction relative to the fixed body, the second spring having a second spring constant different from the first spring constant.

[0165] According to the landing gear configuration of aspect 6, it is possible to suppress the resonance phenomenon of the fuselage at a plurality of frequencies.

[0166] [Aspect 7] The landing gear for a rotary wing aircraft according to any one of Aspects 1 to 6, wherein the at least one spring includes a spring that vibrates in a vertical direction and a spring that vibrates in a direction different from the vertical direction.

[0167] According to the landing gear configuration of aspect 7, not only can vertical vibrations of the rotorcraft fuselage be suppressed, but also vibrations in directions other than the vertical direction.

[0168] [Aspect 8] The landing gear for a rotary wing aircraft according to any one of Aspects 1 to 7, wherein the rigid body includes a cylindrical body, and at least a portion of the spring is disposed inside the cylindrical body.

[0169] According to the landing gear configuration of aspect 8, at least a portion of the spring is disposed inside the cylindrical body, so that at least a portion of the spring can be protected.

[0170] [Aspect 9] A landing gear for a rotary-wing aircraft, comprising: a support including a fixed body fixed to a fuselage of the rotary-wing aircraft; and at least one ground-contacting body that comes into contact with a landing surface when the rotary-wing aircraft is not in flight; and at least one spring that connects the fixed body and the support so that the fixed body and the support can move relative to each other, and that reduces vibration of the fuselage of the rotary-wing aircraft together with the support when the rotary-wing aircraft is in flight, wherein the at least one spring includes a spring that vibrates in a direction different from the up and down direction.

[0171] According to the landing gear configuration of aspect 9, vibrations in directions other than the vertical direction of the rotorcraft fuselage can be suppressed.

[0172] [Aspect 10] A rotorcraft comprising: a fuselage; at least one rotor blade supported on the fuselage; and the landing gear according to any one of aspects 1 to 9.

[0173] DESCRIPTION OF SYMBOLS 1: Rotorcraft 2: Fuselage 3, 110: Landing gear 3A, 3D: Fixed body 3B, 3E: Support body 3C: Ground contact body 6a: Rotor blade 11: Mount body 12: Skid 13, 122: Cross tube 16, 121: Bracket 21, 91, 101, 111: Spring 22, 71, 92, 102, 112: Rigid body 23, 93, 103, 113: Actuator 41, 71b: First engagement structure 42, 84: Second engagement structure 50: Controller 131: Spring D: Dynamic vibration absorber

Claims

1. A landing gear for a rotary-wing aircraft, comprising: a support including a fixed body fixed to a fuselage of the rotary-wing aircraft; and at least one ground-contacting body that comes into contact with a landing surface when the rotary-wing aircraft is not in a flight state; at least one spring that connects the fixed body and the support so that the fixed body and the support can move relative to each other, and that reduces vibration of the fuselage of the rotary-wing aircraft together with the support when the rotary-wing aircraft is in a flight state; and a rigid body that moves relative to at least one of the fixed body and the support between a limiting position that limits the fixed body and the support from approaching each other and a release position that releases the restriction on the fixed body and the support from approaching each other.

2. A landing gear for a rotary-wing aircraft as described in claim 1, wherein the rigid body includes a first engagement structure, one of the fixed body and the support body supports the rigid body, the other of the fixed body and the support body includes a second engagement structure engageable with the first engagement structure, and the limiting position is a position where the first engagement structure and the second engagement structure engage with each other so as to limit the fixed body and the support body from moving away from each other.

3. A landing gear for a rotary wing aircraft according to claim 1 or 2, further comprising an actuator that moves the rigid body between the restricting position and the releasing position.

4. The landing gear for a rotary-wing aircraft of claim 3, further comprising a processing circuit configured to control the actuator, wherein the rigid body is maintained in the restricted position when the rotary-wing aircraft is in the non-flying state, and the processing circuit is configured to: control the actuator to move the rigid body from the restricted position to the released position when the rotary-wing aircraft transitions from the non-flying state to the flying state; and control the actuator to move the rigid body from the released position to the restricted position when the rotary-wing aircraft transitions from the flying state to the non-flying state.

5. A landing gear for a rotary-wing aircraft according to claim 1 or 2, wherein the at least one ground contact body includes a pair of skids spaced apart from each other in the left-right direction, and the support body further includes at least one cross tube connecting the pair of skids.

6. A landing gear for a rotary-wing aircraft as described in claim 1 or 2, wherein the at least one spring includes: a first spring having a first spring constant, connected to the fixed body and the support body so that the support body can vibrate in an up-down direction relative to the fixed body; and a second spring having a second spring constant different from the first spring constant, connected to the fixed body and the support body so that the support body can vibrate in the up-down direction relative to the fixed body.

7. A landing gear for a rotary-wing aircraft according to claim 1 or 2, wherein the at least one spring includes a spring that vibrates in a vertical direction and a spring that vibrates in a direction different from the vertical direction.

8. A landing gear for a rotorcraft according to claim 1 or 2, wherein the rigid body includes a cylindrical body, and at least a portion of the spring is disposed inside the cylindrical body.

9. A landing gear for a rotary-wing aircraft, comprising: a support body including a fixed body fixed to a fuselage of the rotary-wing aircraft; and at least one ground contact body that comes into contact with a landing surface when the rotary-wing aircraft is not in flight; and at least one spring that connects the fixed body and the support body so that the fixed body and the support body can move relative to each other, and that reduces vibration of the fuselage of the rotary-wing aircraft together with the support body when the rotary-wing aircraft is in flight, wherein the at least one spring includes a spring that vibrates in a direction different from the up and down direction.

10. A rotorcraft comprising: a fuselage; at least one rotary wing rotor blade supported on the fuselage; and a landing gear according to claim 1 or 9.

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