Unmanned aerial vehicle retractable front landing gear and unmanned aerial vehicle

Abstract

This invention discloses a retractable front landing gear for a drone and the drone itself, including an actuator and a shock absorber. The telescopic end of the shock absorber is connected to a tire. The actuator is rotatably connected to the fuselage. The output end of the actuator is connected to the shock absorber via a telescopic linkage, and can drive the shock absorber to rotate relative to the fuselage. The shock absorber includes an outer cylinder and an inner cylinder capable of sliding and rotating relative to the outer cylinder. In this invention, by opening normally open holes and unidirectional through holes in the horizontal section of the inner cylinder, the positive and negative damping of the shock absorber is achieved, thus balancing landing cushioning and taxiing vibration reduction functions.

Description

Technical Field

[0001] This invention relates to the field of aircraft landing gear technology, and more specifically to a retractable front landing gear for a drone and the drone itself. Background Technology

[0002] Landing gear is a critical component during the takeoff and landing of unmanned aerial vehicles (UAVs), used to dissipate and absorb energy during landing and braking. Traditional fixed-wing UAVs typically have fixed landing gear due to limitations in space layout, flight time, and weight. This type of landing gear significantly impacts the aerodynamic shape of the airframe, increasing drag and affecting the UAV's flight time.

[0003] Most existing landing gears for small drones in China use spring-dampened landing gear, which is often non-retractable or retractable but has a complex self-locking mechanism and high manufacturing cost. While spring-dampened landing gear is relatively inexpensive, its shock absorption performance is poor, and its cushioning effect varies for drones of different weights, requiring constant spring replacement and adjustment. In contrast, some domestic drones use oil-pneumatic shock absorbers, which have complex structures, numerous parts, high manufacturing difficulty, and high manufacturing cost, making them unsuitable for the development and application of low-cost, serialized drones.

[0004] Document CN103523212A discloses an aircraft nose landing gear, wherein the nose landing gear is mounted on the aircraft structure by two mounting shafts on a shock absorber strut, and the nose landing gear can rotate around the mounting shafts; one end of the retraction strut actuator cylinder has a spherical bearing, which is connected to the shaft of the shock absorber strut and fixed by a nut; the other end of the retraction strut actuator cylinder is mounted on a joint on the fuselage structure via a threaded shaft; the wheel fork is bolted to the inner cylinder of the shock absorber strut; the wheel and tire are mounted on the wheel fork via axles; the upper anti-torsion arm is mounted on a ring joint at its upper end; the lower anti-torsion arm is mounted on the joint of the wheel fork at its lower end; the upper and lower anti-torsion arms are connected by quick-release pins. This design, while ensuring the strength and rigidity of the landing gear, has a simple structure, complete functions, and is suitable for small aircraft. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to integrate landing gear landing cushioning and taxiing vibration reduction and adapt to the cushioning requirements of different impact loads.

[0006] This invention solves the above-mentioned technical problems through the following technical means: A retractable front landing gear for an unmanned aerial vehicle (UAV), comprising an actuator and a shock absorber. The telescopic end of the shock absorber is connected to a tire. The actuator is rotatably connected to the fuselage. The output end of the actuator is transmitted to the shock absorber via a retraction linkage and is capable of driving the shock absorber to rotate relative to the fuselage. The shock absorber includes an outer cylinder and an inner cylinder capable of sliding and rotating relative to the outer cylinder. A sealed cavity is provided inside the outer cylinder, which is filled with aviation hydraulic oil and air. A horizontal section of the inner cylinder extending into the inner cavity of the outer cylinder divides the cavity into an upper cavity. The lower cavity and the horizontal section of the inner cylinder are also provided with a normally open hole and a one-way through hole connecting the upper cavity and the lower cavity; the extension and retraction linkage includes an upper linkage and a lower linkage. One end of the upper linkage is rotatably connected to the machine body through a linkage support, and the other end is rotatably connected to the lower linkage. The output end of the actuator is rotatably connected to the upper linkage. The end of the lower linkage away from the upper linkage is rotatably connected to the outer cylinder, and the end of the outer cylinder away from the inner cylinder is rotatably connected to the machine body. The connection point between the upper linkage and the lower linkage is not located on the line connecting the connection point between the upper linkage and the machine body and the connection point between the lower linkage and the outer cylinder.

[0007] As a preferred technical solution, a top rod is provided on the upper connecting rod, and a retraction and positioning sensor adapted to the top rod is fixedly connected to one end of the connecting rod support facing the upper connecting rod.

[0008] As a preferred technical solution, a stop block is also provided at the end where the lower connecting rod is rotatably connected to the upper connecting rod.

[0009] As a preferred technical solution, a buffer support is fixedly connected to the end of the outer cylinder away from the inner cylinder. The buffer support is provided with two through shafts, and the through shafts are provided with through shaft oil injection nozzles.

[0010] As a preferred technical solution, a steering servo is fixedly connected to the outer cylinder, and a steering collar is rotatably connected to the outer cylinder. The output end of the steering servo is connected to the steering collar and can drive the steering collar to rotate with the outer cylinder axis as the pivot. A wheel fork is fixedly connected to the steering collar, and the tire is rotatably mounted on the wheel fork.

[0011] As a preferred technical solution, the output end of the steering servo is fixedly connected to a rocker arm mounting flange, the rocker arm mounting flange is fixedly connected to one end of the servo rocker arm, and the other end of the servo rocker arm is rotatably connected to the steering collar through a connecting rod, both ends of the connecting rod being ball bearings.

[0012] As a preferred technical solution, the steering collar is rotatably connected to the wheel fork via a swing arm. The swing arm includes an upper swing arm and a lower swing arm. One end of the upper swing arm is rotatably connected to the steering collar, and the other end is rotatably connected to one end of the lower swing arm. The other end of the lower swing arm is rotatably connected to the wheel fork.

[0013] As a preferred technical solution, a cylinder liner is installed between the inner cylinder and the outer cylinder. The cylinder liner is fixedly connected to the inner wall of the bottom of the outer cylinder. Two layers of O-rings are provided on both the inner and outer sides of the cylinder liner. Felt rings are provided on the mating surfaces of the cylinder liner and the vertical section of the inner cylinder.

[0014] As a preferred technical solution, four oil passage holes are provided on the inner cylinder. Two of the oil passage holes are equipped with flow control bolts and form unidirectional guide holes, while the other two oil passage holes form normally open holes.

[0015] The present invention also provides a drone, including the aforementioned retractable front landing gear.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) In this invention, by opening normally open holes and unidirectional through holes on the horizontal section of the inner cylinder, the positive and negative damping of the shock absorber is ensured through this structure, taking into account both landing buffer and taxiing vibration reduction functions. Specifically, when the aircraft lands and compresses: the shock absorber is compressed due to the impact of gravity. The shock absorber is filled with nitrogen gas, which acts like a spring to store energy. Meanwhile, the oil passes through the two normally open holes and two unidirectional through holes at extremely high speed, absorbing a large amount of impact energy and converting it into heat energy, so that the aircraft can land smoothly. When extended: to prevent the nose of the aircraft from bouncing after landing. Because the cavity contains compressed gas after compression, the piston extends, and the oil can only pass through two normally open small holes, which slows down the piston's extension speed, allowing the aircraft to land smoothly without bouncing. The design of the retraction linkage ensures deployment rigidity while reducing the size of the actuator and the load, lowering the system failure rate, and ensuring a stable and controllable retraction trajectory. The connection point between the upper and lower linkages is not located on the line connecting the upper linkage to the fuselage and the lower linkage to the outer cylinder, resulting in an eccentric torque when the landing gear is fully extended. Without external force, the state of the nose landing gear will not change.

[0018] (2) In this invention, by setting the stop block, the push rod and the retraction and extension position sensor, the retraction and extension linkage can have a self-locking function, thereby improving the stability and safety of the aircraft after landing.

[0019] (3) In this invention, two O-rings are arranged inside and outside the cylinder liner to ensure the sealing effect of hydraulic oil and air in the cavity. A felt ring is installed at the bottom of the cylinder liner. The function of the felt ring is to keep the inner cylinder side wall clean and prevent foreign objects from entering the landing gear buffer system and damaging the internal structure of the landing gear. Attached Figure Description

[0020] Figure 1 Schematic diagram of the retractable front landing gear structure for oil and gas buffer;

[0021] Figure 2 Schematic diagram of the retractable and positioning monitoring system for the oil and gas buffer landing gear;

[0022] Figure 3 Schematic diagram of the retractable front landing gear steering mechanism with oil-gas buffer;

[0023] Figure 4 Top sectional view of the retractable front landing gear buffer mechanism for oil and gas cushioning;

[0024] Figure 5 Front sectional view of the retractable front landing gear buffer mechanism for oil and gas cushioning;

[0025] Figure 6 Schematic diagram of the retractable front landing gear with oil and gas buffer in the retracted state;

[0026] Reference numerals: 1. Retraction / Extension Position Sensor; 2. Push Rod; 3. Upper Connecting Rod; 4. Lower Connecting Rod; 5. Steering Servo Mounting Bracket; 6. Steering Collar Lubricating Inlet; 7. Cylinder Liner Retaining Ring; 8. Inner Cylinder; 9. Wheel Fork; 10. Wheel Axle; 11. Connecting Rod Support; 12. Actuator; 13. Through Shaft Lubricating Inlet; 14. Through Shaft; 15. Outer Cylinder; 16. Steering Servo; 17. Upper Control Arm; 18. Lower Control Arm; 19. Wheel Hub; 20. Tire; 21. Rocker Arm Mounting Flange; 22. Servo Rocker Arm; 23. Connecting Rod; 24. Steering Collar; 25. Hydraulic Oil Lubricating Inlet; 26. Spring; 27. Cylinder Liner; 28. Cavity; 29. ​​Flow Control Bolt; 30. Nylon Felt Ring; 31. O-ring Seal; 32. Felt Ring; 33. Oil Pass Hole; 34. Stop Block. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] See Figure 1 , Figure 5A retractable nose landing gear for an unmanned aerial vehicle (UAV) includes an actuator 12 and a shock absorber. The telescopic end of the shock absorber is connected to a tire 20. The actuator 12 is rotatably connected to the fuselage. The output end of the actuator 12 is connected to the shock absorber via a retraction linkage and can drive the shock absorber to rotate relative to the fuselage. The shock absorber includes an outer cylinder 15 and an inner cylinder 8 that can slide and rotate relative to the outer cylinder 15. A sealed cavity 28 is provided inside the outer cylinder 15, filled with aviation hydraulic oil and air. The horizontal section of the inner cylinder 8 extending into the inner cavity of the outer cylinder 15 divides the cavity 28 into an upper cavity and a lower cavity. The horizontal section of the cylinder 8 is also provided with a normally open hole and a unidirectional through hole connecting the upper cavity and the lower cavity; in this embodiment, four oil passage holes 33 are provided on the inner cylinder 8, which are distributed at equal angles along the center of the inner cylinder 8, but the number and arrangement are not limited to this. Two oil passage holes 33 are provided with flow control bolts 29 and form unidirectional through holes, and the other two oil passage holes 33 form normally open holes. The flow control bolts 29 are existing technology. When the landing gear rebounds, the flow control bolts 29 block the oil passage holes 33 under the action of hydraulic oil, thereby changing the flow rate of hydraulic oil entering and exiting, and realizing the buffer function.

[0029] The head of the flow control bolt 29 is elastically connected to the upper surface of the horizontal section of the inner cylinder 8 via a spring 26. One end of the spring 26 is fixedly connected to the head of the flow control bolt 29, and the other end is fixedly connected to the horizontal section of the inner cylinder 8. A nut is fixedly connected to one end of the flow control bolt 29 that extends out of the oil passage 33 and into the lower cavity. A washer is also provided between the nut and the lower surface of the horizontal section of the inner cylinder 8. The spring 26 is mainly used to control the opening and closing of the two variable oil holes, thereby controlling the flow rate of hydraulic oil during compression and extension, playing a buffering role and reducing rebound. The spring 26 is located on the outside of the rod of the flow control bolt 29. In the static state, the washer and the nut are tightly attached to the lower surface of the inner cylinder 8 under the action of the spring 26. When the landing gear is compressed, the oil can overcome the elastic force and pass through the one-way guide hole. When extended, the washer is attached to the lower surface of the inner cylinder 8, and the one-way guide hole is in a closed state, reducing the hydraulic oil flow and preventing excessive rebound.

[0030] This structure ensures both positive and negative damping of the shock absorber, taking into account both landing buffering and taxiing vibration reduction functions. Specifically, during the compression phase of aircraft landing: the shock absorber is compressed due to the impact of gravity. The shock absorber is filled with nitrogen gas, which acts like a spring, storing energy. Meanwhile, the oil passes through two normally open holes and two unidirectional through holes at extremely high speed, absorbing a large amount of impact energy and converting it into heat energy, so that the aircraft can land smoothly. During the extension phase: to prevent the nose of the aircraft from bouncing after landing, the compressed gas in the cavity after compression causes the piston, i.e., the inner cylinder 8, to extend. The oil can only pass through two normally open small holes, which slows down the speed of piston extension, allowing the aircraft to land smoothly without bouncing.

[0031] See Figure 1 , Figure 2The retraction linkage includes an upper linkage 3 and a lower linkage 4. One end of the upper linkage 3 is rotatably connected to the fuselage via a first rotating shaft and a linkage support 11, while the other end is rotatably connected to the lower linkage 4 via a second rotating shaft. The output end of the actuator 12 is rotatably connected to the upper linkage 3. The end of the lower linkage 4 facing away from the upper linkage 3 is rotatably connected to the outer cylinder 15 via a third rotating shaft. The outer cylinder 15 is equipped with a hydraulic oil injection nozzle 25, which communicates with the inner cavity of the outer cylinder 15, i.e., with the upper and lower cavities. Aviation hydraulic oil and compressed air are injected through the hydraulic oil injection nozzle 25. The outer cylinder 15, at the end opposite to the inner cylinder 8, is rotatably connected to the fuselage. The connection point between the upper connecting rod 3 and the lower connecting rod 4 is not located on the line connecting the upper connecting rod 3 and the fuselage to the lower connecting rod 4 and the outer cylinder 15. That is, the second rotating shaft is not on the line connecting the center points of the first and third rotating shafts. Alternatively, the line connecting the center of the first and second rotating shafts can be angled, creating an eccentric torque after the landing gear is fully extended. Without external force, the state of the nose landing gear will not change. This improves the stability and safety of the aircraft after landing. A top rod 2 is fixedly connected to the upper connecting rod 3. A retraction / extension sensor 1, adapted to the top rod 2, is fixedly connected to the end of the connecting rod support 11 facing the upper connecting rod 3. When the top rod 2 contacts the retraction / extension sensor 1, it is in the retracted state; when not in contact, it is in the extended or lowered state. Figure 6 As shown, after takeoff, the nose landing gear retracts into the fuselage under the action of the retraction actuator 12. A push rod 2 is arranged at the end of the upper retraction linkage 3. After the push rod 2 contacts the retraction positioning sensor 1, it generates a signal. After the flight control computer receives the signal, the ground personnel can accurately and quickly determine the status of the nose landing gear based on the signal. A stop block 34 is also provided at the end of the lower linkage 4 that is rotatably connected to the upper linkage 3. The stop block 34 is mainly used to limit the upper linkage 3 so that it does not continue to move downward and prevents the landing gear from lowering at an excessive angle.

[0032] A buffer support is fixedly connected to one end of the outer cylinder 15 away from the inner cylinder 8. Two through shafts 14 are provided on the buffer support, and through shaft oil nozzles 13 are provided on the through shafts 14. The buffer support is rotatably connected to the machine body through the through shafts 14.

[0033] See Figure 3 , Figure 5Two steering servo mounting brackets 5 are fixedly connected to the outer cylinder 15. A steering servo 16 is fixedly connected to the steering servo mounting bracket 5. A steering collar 24 is rotatably connected to the outer cylinder 15. A steering collar grease nipple 6 is provided on the steering collar 24. A cylinder liner retaining ring 7 is fixedly connected to the outer cylinder 15 to limit the movement of the steering collar 24. The output end of the steering servo 16 is connected to the steering collar 24 and can drive the steering collar 24 to rotate around the axis of the outer cylinder 15. A wheel fork 9 is fixedly connected to the steering collar 24. The tire 20 is rotatably connected to the wheel fork 9 through a wheel axle 10. A wheel hub 19 is rotatably connected to the wheel axle 10 and fixed to the inner ring of the tire 20. The output end of the steering servo 16 is fixedly connected to... There is a rocker arm mounting flange 21, which is fixedly connected to one end of the servo rocker arm 22. The other end of the servo rocker arm 22 is rotatably connected to the steering collar 24 through the connecting rod 23. Both ends of the connecting rod 23 are ball bearings. The steering collar 24 is rotatably engaged with the wheel fork 9 through the anti-sway arm. The anti-sway arm includes an upper swing arm 17 and a lower swing arm 18. One end of the upper swing arm 17 is rotatably connected to the steering collar 24, and the other end is rotatably connected to one end of the lower swing arm 18. The other end of the lower swing arm 18 is rotatably connected to the wheel fork 9. When the aircraft lands, the inner cylinder 8 is compressed into the outer cylinder 15 under the action of the aircraft's gravity. The angle between the upper swing arm 17 and the lower swing arm 18 is correspondingly compressed, which can effectively prevent the aircraft's nose wheel from swaying and improve the stability of the aircraft landing.

[0034] See Figure 4 , Figure 5 A cylinder liner 27 is installed between the inner cylinder 8 and the outer cylinder 15. The cylinder liner 27 is fixedly connected to the inner wall of the bottom of the outer cylinder 15. Two layers of O-rings 31 are provided on both the inner and outer sides of the cylinder liner 27, which are arranged radially along the cylinder liner 27. Felt rings 32 are provided on the mating surface between the cylinder liner 27 and the vertical section of the inner cylinder 8. The function of the felt rings 32 is to keep the side wall of the inner cylinder 8 clean and prevent foreign objects from entering the landing gear buffer system and damaging the internal structure of the landing gear. Nylon felt rings 30 are arranged on the side wall of the inner cylinder 8 to ensure the sealing performance of the upper and lower cavities and to serve as a lubricant.

[0035] It should be noted that this embodiment also provides a drone including a retractable front landing gear.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A retractable front landing gear for an unmanned aerial vehicle (UAV), comprising an actuator (12) and a shock absorber, wherein the telescopic end of the shock absorber is connected to a tire (20), characterized in that, The actuator (12) is rotatably connected to the fuselage. The output end of the actuator (12) is connected to the shock absorber via the retraction link and can drive the shock absorber to rotate relative to the fuselage. The shock absorber includes an outer cylinder (15) and an inner cylinder (8) that can slide and rotate relative to the outer cylinder (15). The outer cylinder (15) has a sealed cavity (28) filled with aviation hydraulic oil and air. The horizontal section of the inner cylinder (8) extending into the inner cavity of the outer cylinder (15) divides the cavity (28) into an upper cavity and a lower cavity. The horizontal section of the inner cylinder (8) also has a normally open hole and a one-way through hole connecting the upper cavity and the lower cavity. The retraction link includes an upper link (3) and a lower link (4). One end of the upper link (3) is connected to the fuselage via a link support (11). The body is rotatably connected, and the other end is rotatably connected to the lower connecting rod (4). The output end of the actuator (12) is rotatably connected to the upper connecting rod (3). The end of the lower connecting rod (4) away from the upper connecting rod (3) is rotatably connected to the outer cylinder (15). The end of the outer cylinder (15) away from the inner cylinder (8) is rotatably connected to the fuselage. The connection point between the upper connecting rod (3) and the lower connecting rod (4) is not located on the line connecting the connection point between the upper connecting rod (3) and the fuselage and the connection point between the lower connecting rod (4) and the outer cylinder (15). A buffer support is fixedly connected to the end of the outer cylinder (15) away from the inner cylinder (8). Two through shafts (14) are provided on the buffer support. Through shaft oil nozzles (13) are provided on the through shafts (14). A steering servo (16) is fixedly connected to the outer cylinder (15). A steering collar (24) is rotatably connected to the cylinder (15). The output end of the steering servo (16) is connected to the steering collar (24) and can drive the steering collar (24) to rotate around the axis of the outer cylinder (15). The steering collar (24) is connected to a wheel fork (9), and the tire (20) is rotatably mounted on the wheel fork (9). The output end of the steering servo (16) is fixedly connected to a rocker arm mounting flange (21). The rocker arm mounting flange (21) is fixedly connected to one end of the servo rocker arm (22). The other end of the servo rocker arm (22) is rotatably connected to the steering collar (24) through a connecting rod (23). Both ends of the connecting rod (23) are ball bearings. The steering collar (24) is rotatably engaged with the wheel fork (9) through a swing arm. The swing arm includes an upper... The upper swing arm (17) and the lower swing arm (18) are connected to the steering collar (24) at one end and to the lower swing arm (18) at the other end. The lower swing arm (18) is connected to the wheel fork (9) at the other end. A cylinder liner (27) is installed between the inner cylinder (8) and the outer cylinder (15). The cylinder liner (27) is fixedly connected to the inner wall of the bottom of the outer cylinder (15). Two O-rings (31) are provided on both the inner and outer sides of the cylinder liner (27). Felt rings (32) are provided on the mating surface of the cylinder liner (27) and the vertical section of the inner cylinder (8). Four oil passage holes (33) are provided on the inner cylinder (8). Two oil passage holes (33) are provided with flow control bolts (29) and form unidirectional through holes. The other two oil passage holes (33) form normally open holes.

2. The retractable front landing gear of a drone according to claim 1, characterized in that, The upper connecting rod (3) is provided with a top rod (2), and the connecting rod support (11) facing the upper connecting rod (3) is fixedly connected with a retraction and placement sensor (1) that is compatible with the top rod (2).

3. The retractable front landing gear of a drone according to claim 1, characterized in that, The lower connecting rod (4) is rotatably connected to the upper connecting rod (3) and a stop block (34) is also provided at one end.

4. A drone, characterized in that, Including a retractable front landing gear for a drone as described in any one of claims 1-3.

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