Military attack unmanned aerial vehicle nose landing gear folding and unfolding system

Abstract

The invention discloses a military attack unmanned aerial vehicle nose landing gear folding and unfolding system which comprises a front fuselage, a nose landing gear, a nose landing gear cabin door and a nose landing gear supporting shaft, the nose landing gear supporting shaft is combined and fixed with a nut through a regular hexagon end face and a mounting groove, and the nose landing gear is connected with the nose landing gear supporting shaft in a sleeved mode through a deep groove ball bearing. The nose landing gear integrates hydraulic damping, steering adjusting and hydraulic folding and unfolding functions, a hydraulic damping cylinder is arranged in a main rod to relieve lifting impact, a steering mechanism can drive airplane wheels to achieve steering, folding and unfolding of the nose landing gear are achieved through cooperative action of a hydraulic connecting rod and a hydraulic actuating cylinder, and a cabin door of the nose landing gear is driven by a double-acting hydraulic rod. The rubber sealing piece is arranged on the edge and is flush with the fuselage skin after being closed, and the pneumatic integrity and the sealing protection effect are achieved. The device is stable in structure and reliable in folding and unfolding, the flight aerodynamic resistance is effectively reduced, the stealth performance is enhanced, and the tactical use requirement of a large-load military attack unmanned aerial vehicle can be met.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) technology, specifically to a nose landing gear retraction and extension system for a military attack UAV, applicable to military reconnaissance and strike UAVs requiring high maneuverability and low flight drag. Background Technology

[0002] Military attack drones play a crucial role in modern warfare, undertaking key missions such as precision strikes and reconnaissance surveillance. Their landing gear system, as a core component ensuring safe takeoff and landing, directly impacts the drone's combat effectiveness and mission success rate. The nose landing gear, as a vital part of the landing gear system, not only needs to withstand the impact loads during takeoff and landing but also needs to reliably extend and retract during flight to reduce aerodynamic drag and avoid affecting the drone's flight speed, maneuverability, and stealth capabilities.

[0003] Currently, the nose landing gear systems of different types of aircraft have many compatibility defects, making it difficult to meet the tactical requirements of military attack drones. The nose landing gear retraction mechanism commonly used in light sport aircraft mostly adopts a worm gear mechanical transmission scheme driven by a handle. It relies on manual operation and cannot achieve unmanned automatic retraction. Moreover, the transmission chain is long and there are many points of failure. For example, the nose landing gear retraction mechanism for light sport aircraft with publication number CN211076320U has a spring-type shock absorption component that can only buffer low-frequency small-amplitude impacts and cannot cope with the high-intensity loads of complex battlefields. At the same time, it lacks a dedicated landing gear bay and sealing design, resulting in high aerodynamic drag and easy entry of foreign objects.

[0004] Although the nose landing gear of some heavy-load aircraft has hydraulic retraction and extension capabilities, such as the aircraft nose landing gear structure and retraction and extension method disclosed in CN120308332A, its anti-sway component adopts a split friction structure. With long-term use, the anti-sway damping is prone to instability due to loose bolts. The retraction and extension control component relies on the linkage between the lever arm and the spring, without precise angle limit and emergency retraction capability. Moreover, each functional module is scattered and independent, without coordinated control logic, and does not take into account the needs of stealth and rapid battlefield maintenance.

[0005] Furthermore, existing UAV nose landing gear structures are mostly suitable for small models, and most cannot be fully retracted into the fuselage. This fails to meet the load-bearing requirements of larger, heavier aircraft and makes it difficult to achieve the tactical objectives of high maneuverability and low drag. To address these issues, there is an urgent need to design a stable, reliable, aerodynamically efficient nose landing gear retraction and extension system for military attack UAVs, adaptable to complex military operating conditions, to meet the tactical requirements of military attack UAVs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a front landing gear retraction and extension system for military attack drones.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a nose landing gear retraction and extension system for a military attack unmanned aerial vehicle, including a front fuselage, a nose landing gear, a nose landing gear door, and a nose landing gear support shaft; The forward fuselage includes a fuselage frame and fuselage skin. The nose landing gear support shaft is fixed to the fuselage frame by a combination structure of polygonal end faces and nuts. Two nose landing gear doors and a control mechanism for driving the opening and closing of the nose landing gear doors are rotatably installed at the bottom of the forward fuselage. The front landing gear includes wheels, a steering mechanism, a main rod, hydraulic shock absorbers, a front fork, and a drive mechanism for rotating the main rod; wherein the steering mechanism includes a steering sleeve, a steering knuckle arm, a steering gear, and a steering drive device; The main rod has symmetrical inclined arms on both sides at the upper end, and the end of the inclined arm is provided with a mounting cylinder. The mounting cylinder is sleeved with the front landing gear support shaft through a fixed bearing. Under the action of the rotational torque provided by the drive mechanism, the front landing gear can rotate around the front landing gear support shaft. The fork is equipped with a wheel, and the upper end of the fork is provided with two sets of fork arms, namely the first set of fork arms and the second set of fork arms, wherein the second set of fork arms is a movable fork arm; The lower end of the main rod is rotatably mounted with a hydraulic shock absorber via a bearing. The lower connecting end of the hydraulic shock absorber is rotatably connected to the second set of forks. The first set of forks is rotatably connected to the lower end of the steering knuckle arm. The upper end of the steering knuckle arm is provided with a steering sleeve with a steering gear on its outer circumferential wall. The steering sleeve is sleeved with the main rod via a bearing. The steering drive device includes a steering motor, which is fixedly mounted on the main shaft, and the output end of the steering motor is provided with a power gear that meshes with the steering gear. The drive mechanism includes a hydraulic connecting rod, a hydraulic actuator, and a support rod. The support rod includes a first herringbone rod, the confluence of which is fixed to the frame and a threaded cylinder is provided at the confluence. The forked end of the first herringbone bar has a mounting hole, which is connected to the front landing gear support shaft via a bearing. The bifurcated ends of the first herringbone rod extend upward and converge again to form the second herringbone rod. A positioning cylinder is provided at the intersection of the second herringbone rod. The cylinder body of the hydraulic actuator is axially positioned by the positioning cylinder. Its shell end is fixedly assembled with the threaded cylinder by threads. The output end of the hydraulic actuator is hinged to one end of the hydraulic connecting rod, and the other end of the hydraulic connecting rod is hinged to the main rod.

[0008] Furthermore, the threaded cylinder has a threaded hole inside, the positioning cylinder has a positioning hole inside, the cylinder body of the hydraulic actuator passes through the positioning hole, and its shell end is fixedly connected to the threaded hole by threads.

[0009] Furthermore, both the first and second herringbone rods are equipped with hollow structures.

[0010] Furthermore, the inner ring of the fixed bearing is interference-fitted with the front landing gear support shaft, and the outer ring of the fixed bearing is interference-fitted with the mounting hole of the mounting cylinder.

[0011] Furthermore, the fixed bearing is a deep groove ball bearing, and the dust covers on both sides of it fit tightly against the inner wall of the mounting hole of the mounting cylinder.

[0012] Furthermore, the polygonal end face has a regular hexagonal structure, and the fuselage frame is provided with a hexagonal mounting groove that matches the regular hexagonal end face.

[0013] Furthermore, the control mechanism includes a double-acting hydraulic rod. The two ends of the two nose landing gear doors are connected to the fuselage frame via a front hinge and a rear hinge, respectively. Both the front hinge and the rear hinge include a base, a hinge shaft, and an arc-shaped connector. The base is mounted on the fuselage frame. One end of the arc-shaped connector is hinged to the base via the hinge shaft, and the other end is fixedly connected to the inner surface of the nose landing gear door. The front hinge also includes a connecting plate set on the arc-shaped connector. One end of the double-acting hydraulic rod is mounted on the machine frame through a hinge seat, and the other end is hinged to the connecting plate. When the double-acting hydraulic rod is in operation, it drives the arc-shaped connecting piece to rotate around the hinge axis through the connecting plate, thereby driving the nose landing gear door to open and close at a preset angle.

[0014] Furthermore, the rotation angle range of the nose landing gear around the nose landing gear support axis is 0°-77°, with 0° corresponding to the nose landing gear in the lowered state and 77° corresponding to the nose landing gear in the retracted state.

[0015] Furthermore, a rubber seal is provided on the mating surface between the nose landing gear door and the fuselage skin, and a groove for accommodating the rubber seal is provided on the edge of the nose landing gear door.

[0016] Furthermore, both the front and rear hinges are made of stainless steel. Beneficial effects

[0017] 1. The present invention provides two sets of fork arms on the front fork. The first set of fork arms is linked to the steering mechanism, and the second set of fork arms is a movable fork arm connected to the hydraulic shock absorber. This achieves mechanical decoupling of shock absorption and steering functions, allowing the shock absorption system to focus on absorbing vertical impact loads, while the steering mechanism independently controls directional adjustment. The two do not interfere with each other, significantly improving the reliability of the landing gear under complex working conditions.

[0018] 2. The drive mechanism adopts a sequential operation of hydraulic actuator and hydraulic connecting rod (actuator takes priority when retracting, connecting rod takes priority when lowering), which, together with the stable fixation of the support rod, realizes controllable retraction and extension actions without the need for additional complex drive components, and is suitable for the use of military drones with large payloads.

[0019] 3. The front landing gear support shaft is fixed with a polygonal end face and a nut, and with the double interference fit of the fixed bearing (inner ring to support shaft, outer ring to mounting hole), it ensures both the freedom of rotation and the stability of the structure, so that the front landing gear can only rotate around the support shaft, and achieves smooth extension and retraction within the preset angle range.

[0020] 4. By setting up a sealed and dustproof deep groove ball bearing (the dust cover fits tightly against the inner wall of the mounting hole), dust and grit are effectively blocked from entering, reducing the risk of wear and lubrication failure caused by contamination, reducing maintenance frequency and extending bearing life, and ensuring the stable operation of the drone in harsh environments.

[0021] 5. The front landing gear door is opened and closed by a double-acting hydraulic rod. The arc-shaped connecting piece is precisely driven to rotate around the hinge axis through the connecting plate, which ensures the synchronicity and consistency of the door opening and closing. This avoids the unstable return problem that may exist in single-acting hydraulic rods and enhances the system's response capability and reliability under complex working conditions.

[0022] 6. By installing rubber seals and edge grooves on the mating surface between the nose landing gear bay door and the fuselage skin, the door is flush with the skin when closed, effectively eliminating additional aerodynamic drag during flight, improving the stealth performance of the UAV, preventing foreign objects from entering the landing gear bay, and ensuring aerodynamic integrity.

[0023] 7. By setting hollowed-out first and second herringbone rods on the front fork, the weight can be reduced without affecting the structural strength, thereby optimizing the drone's maneuverability and fuel efficiency.

[0024] 8. The use of unpowered landing gear reduces the overall weight of the fuselage, while the friction between the rubber material and the runway absorbs impact, providing direct and efficient shock absorption. These innovative designs work together to significantly improve the reliability, stealth, shock absorption performance, and maneuverability of the military attack UAV's nose landing gear system, meeting the requirements of high-mobility operations, while reducing maintenance costs and extending service life. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the front landing gear. Figure 3 This is a schematic diagram showing the connection between the hydraulic connecting rod and the hydraulic actuator cylinder; Figure 4 This is a schematic diagram of the structure when the front landing gear is retracted. Figure 5 This is a schematic diagram of the nose landing gear retraction process of the present invention; Figure 6 This is a schematic diagram of the front landing gear retracting into the front fuselage of the present invention; Figure 7 This is a schematic diagram showing the wheel turning to the left. Figure 8 This is a schematic diagram showing the wheel turning to the right. Figure 9 This is a schematic diagram of the nose landing gear retraction process. Figure 10 A frame diagram showing the front landing gear fully extended; Figure 11 This is a partial structural diagram of the nose landing gear bay door when it is open. Figure 12 This is a partial structural diagram of the nose landing gear bay door when it is closed. Figure 13 This is a control diagram of the nose landing gear bay door; Figure 14 This is a schematic diagram showing the installation of the steering mechanism and the front fork. Figure 15 This is a structural diagram of the support rod; Figure 16 This is a schematic diagram of the steering drive unit installation. In the diagram: 1. Forward fuselage; 2. Front landing gear; 3. Fuselage skin; 4. Fuselage frame; 5. Front landing gear door; 6. Front landing gear support shaft; 7. Wheel; 8. Steering mechanism; 9. Main rod; 10. Hydraulic shock absorber; 11. Hydraulic connecting rod; 12. Hydraulic actuator; 13. Support rod; 14. Connecting bolt; 15. Hinge bolt; 16. Front fork; 17. Steering drive unit; 51. Double-acting hydraulic rod; 52. Front hinge; 53. Rear hinge; 54. Rubber seal; 81. Steering sleeve; 82. Steering knuckle arm. Steering gear 83, slant arm 91, mounting cylinder 92, first herringbone rod 131, second herringbone rod 132, mounting hole 133, first set of fork arm 161, second set of fork arm 162, steering motor 171, power gear 172, fixing steel strip 173, fixing bolt 174, base 531, hinge shaft 532, arc-shaped connector 533, connecting plate 534, threaded cylinder 1311, threaded hole 1312, positioning cylinder 1321, positioning hole 1322. Detailed Implementation

[0026] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0027] Example: Figure 1-16As shown, the present invention provides a nose landing gear retraction system for a military attack unmanned aerial vehicle, including a front fuselage 1, a nose landing gear 2, a nose landing gear door 5, and a nose landing gear support shaft 6; the front fuselage 1 includes a fuselage frame 4 and a fuselage skin 3, the fuselage frame 4 is the main support body, used to support and fix the fuselage skin 3, the nose landing gear support shaft 6 is fixed to the fuselage frame 4 by a combination structure of polygonal end face and nut, the polygonal end face fits and is positioned with the corresponding mounting surface of the fuselage frame 4, and the axial locking of the nut can realize the constraint of the nose landing gear support shaft 6 inside the fuselage, so that it has no axial movement or circumferential rotation; two nose landing gear doors 5 and a control mechanism for driving the opening and closing of the nose landing gear doors 5 are rotatably installed at the bottom of the front fuselage 1; The front landing gear 2 includes wheels 7, steering mechanism 8, main rod 9, hydraulic shock absorber 10, front fork 16, and drive mechanism for driving the main rod 9 to rotate; the steering mechanism 8 is used to achieve precise direction, and the steering mechanism 8 includes steering sleeve 81, steering knuckle arm 82, steering gear 83, and steering drive device 17. The main rod 9 is the core load-bearing component of the front landing gear 2. The upper end of the main rod 9 is symmetrically provided with inclined arms 91 on both sides. The end of the inclined arms 91 is provided with a mounting cylinder 92. The mounting cylinder 92 is sleeved with the front landing gear support shaft 6 through a fixed bearing. Under the action of the rotational torque provided by the drive mechanism, the front landing gear 2 can rotate around the front landing gear support shaft 6. The fork 16 is equipped with a wheel 7, and the upper end of the fork 16 is provided with two sets of fork arms. The first set of fork arms 161 is on the same straight line as the end of the fork 16, and the second set of fork arms 162 is a movable fork arm. The lower end of the main rod 9 is rotatably mounted with a hydraulic shock absorber 10 via a bearing. The hydraulic shock absorber 10 is used to buffer the ground impact load during takeoff and landing, and improve the shock absorption performance of the landing gear. The lower connecting end of the hydraulic shock absorber 10 is rotatably connected to the second set of fork arms 162. The first set of fork arms 161 is rotatably connected to the lower end of the steering knuckle arm 82. The upper end of the steering knuckle arm 82 is provided with a steering sleeve 81 with a steering gear 83 on its outer circumferential wall. The steering sleeve 81 and the steering gear 83 are sleeved with the main rod 9 via a bearing. By setting two sets of fork arms on the front fork, the mechanical decoupling of shock absorption and steering functions can be effectively achieved: the second set of fork arms 162 is rotatably connected to the hydraulic shock absorber 10, which is specifically used to absorb the vertical impact load during takeoff and landing, and avoids lateral forces interfering with the shock absorption performance; while the first set of fork arms 161 is linked with the steering system through the steering knuckle arm 82 to ensure accurate response of steering actions. This division of labor design significantly improves the reliability of the landing gear under complex operating conditions—the shock absorption system focuses on buffering ground impacts, while the steering mechanism independently controls the direction, and the two do not interfere with each other, thereby enhancing the stability and maneuverability of the UAV during high-speed maneuvers and bumpy landings. The steering drive device 17 includes a steering motor 171, which is fixedly mounted on the main rod 9. The output end of the steering motor 171 is provided with a power gear 172 that meshes with the steering gear 83. Preferably, the steering motor 171 is a high-torque motor. The steering motor 171 is mounted on a motor mount on the upper side of the main rod 9 by means of a fixed steel belt 173 and a fixed bolt 174. The drive mechanism includes a hydraulic connecting rod 11, a hydraulic actuator 12, and a support rod 13; The support rod 13 includes a first herringbone rod 131, the confluence end of which is fixed to the fuselage frame 4 and is provided with a threaded cylinder 1311; the forked end of the first herringbone rod 131 is provided with a mounting hole 133, which is sleeved with the front landing gear support shaft 6 through a bearing; the forked end of the first herringbone rod 131 extends upward and confluences again to form a second herringbone rod 132, and a positioning cylinder 1321 is provided at the confluence of the second herringbone rod 132. The cylinder body of the hydraulic actuator 12 is axially positioned by the positioning cylinder 1321. Its shell end is fixedly assembled with the threaded cylinder 1311 by threads. The output end of the hydraulic actuator 12 is hinged to one end of the hydraulic connecting rod 11, and the other end of the hydraulic connecting rod 11 is hinged to the main rod 9, thereby effectively transmitting the resultant force of the hydraulic connecting rod 11 and the hydraulic actuator 12 to the fuselage structure. The hydraulic actuator 12 is fixed to the support rod 13, which restricts the movement state of the hydraulic actuator 12. The hydraulic drive ensures that the action is controllable, without the need for additional complex drive components, and is suitable for the use needs of military UAVs with large payloads.

[0028] In an optional embodiment, the threaded cylinder 1311 has a threaded hole 1312, the positioning cylinder 1321 has a positioning hole 1322, the cylinder body of the hydraulic actuation cylinder 12 passes through the positioning hole 1322, and its shell end is fixedly connected to the threaded hole 1312 by threads.

[0029] In an optional embodiment, both the first herringbone rod 131 and the second herringbone rod 132 are provided with a hollow structure, which can reduce weight.

[0030] In an optional embodiment, the inner ring of the fixed bearing is interference-fitted with the front landing gear support shaft 6, and the outer ring of the fixed bearing is interference-fitted with the mounting hole of the mounting cylinder 92. This double interference fit ensures both the freedom of rotation and the stability of the structure, ensuring that the front landing gear 2 can only rotate around the support shaft 6, thereby achieving smooth retraction and extension within a preset angle range.

[0031] In an optional embodiment, the fixed bearing is a deep groove ball bearing, with dust covers on both sides tightly fitted to the inner wall of the mounting hole of the mounting cylinder 92, forming a highly efficient sealing and dustproof structure. This design effectively prevents dust, grit, and other foreign objects from entering the bearing, significantly reducing the risk of wear and lubrication failure caused by contamination, thereby reducing maintenance frequency and extending bearing life. Simultaneously, the sealing structure ensures stable bearing operation in complex environments (such as dust and humidity), improving the overall reliability of the landing gear and providing support for the high-mobility operation of UAVs under harsh conditions.

[0032] In an optional embodiment, the polygonal end face is a regular hexagonal structure, and the fuselage frame 4 is provided with a hexagonal mounting groove that matches the regular hexagonal end face.

[0033] In an optional embodiment, the control mechanism includes a double-acting hydraulic rod 51. The two ends of the two nose landing gear doors 5 are connected to the fuselage frame 4 via a front hinge 52 and a rear hinge 53, respectively. Both the front hinge 52 and the rear hinge 53 include a base 531, a hinge shaft 532, and an arc-shaped connector 533. The base 531 is mounted on the fuselage frame 4. One end of the arc-shaped connector 533 is hinged to the base 531 via the hinge shaft 532, and the other end is fixedly connected to the inner surface of the nose landing gear doors 5. The front hinge 52 also includes a connecting plate 534 disposed on the arc-shaped connector 533. One end of the double-acting hydraulic rod 51 is mounted on the machine frame 4 through a hinge seat, and the other end is hinged to the connecting plate 534. When the double-acting hydraulic rod 51 is in operation, it drives the arc-shaped connecting piece 533 to rotate around the hinge axis 532 via the connecting plate 534, thereby driving the nose landing gear door 5 to open and close at a preset angle. The double-acting hydraulic rod provides bidirectional controllable driving force, and the connecting plate 534 precisely drives the arc-shaped connecting piece 533 to rotate around the hinge axis 532, thus stably and reliably controlling the nose landing gear door 5 to open and close at the preset angle. This design ensures the synchronicity and consistency of the door opening and closing, avoids the unstable return problem that may exist with single-acting hydraulic rods, and its bidirectional pressure characteristics also enhance the system's response capability and reliability under complex operating conditions.

[0034] In an optional embodiment, the rotation angle of the front landing gear 2 around the front landing gear support shaft 6 is in the range of 0°-77°, where 0° corresponds to the front landing gear 2 in the lowered state and 77° corresponds to the front landing gear 2 in the retracted state.

[0035] In an optional embodiment, a rubber seal 54 is provided on the mating surface between the nose landing gear door 5 and the fuselage skin 3, and a groove for accommodating the rubber seal is provided on the edge of the nose landing gear door 5. When both nose landing gear doors 5 are closed, they can remain flush with the fuselage skin 3. Through the tight fit of the edge elastic seal, not only can additional aerodynamic drag during flight be effectively eliminated and the stealth performance of the UAV be improved to meet the requirements of high-maneuverability operations, but also aerodynamic integrity can be ensured and foreign objects in the landing gear bay can be prevented from entering, thereby improving the overall service life of the system.

[0036] In an optional embodiment, both the front hinge 52 and the rear hinge 53 are made of stainless steel.

[0037] The working principle of the landing gear of this invention: The working principle of this invention is based on the coordinated control of the hydraulic actuator and the hydraulic connecting rod to realize the linkage between the retraction and extension of the nose landing gear and the cabin door. The specific process is as follows: Landing gear retraction process: When the landing gear retracts, the hydraulic actuator 12 operates first, and the hydraulic oil inside pushes the hydraulic rod to extend axially. This extension, via the hinge bolt 15, drives the hydraulic connecting rod 11 to move axially. The hydraulic connecting rod 11 is hinged to the main rod 9 via the connecting bolt 14, and its axial movement is converted into the upward rotation of the main rod 9 around the front landing gear support shaft 6, causing the landing gear to enter the pre-retracted state (e.g., Figure 5 (As shown); then the hydraulic actuator 12 extends, the hydraulic oil inside the hydraulic connecting rod 11 decreases, generating tension, which continues to pull the main rod 9 upward, finally retracting the landing gear completely into the cabin (as shown). Figure 6 (As shown); During this process, the nose landing gear door 5 remains closed. After the landing gear is fully retracted, the control system drives the nose landing gear door 5 to close, ensuring pneumatic sealing. It should be noted that the hydraulic connecting rod 11 and the hydraulic actuator 12 do not work simultaneously during the landing gear retraction process. Instead, the hydraulic actuator 12 works first, and the hydraulic connecting rod 11 only starts working after the hydraulic actuator 12 completes the retraction process, until the landing gear is fully retracted into the cabin.

[0038] Process under the landing gear: When the landing gear is lowered, the hydraulic connecting rod 11 operates first, and the hydraulic oil inside pushes the hydraulic rod to extend axially. Through the connecting bolt 14, it drives the main rod 9 to rotate downward around the support shaft 6, so that the landing gear enters the pre-extension state (e.g., Figure 9 (As shown); then the hydraulic connecting rod 11 extends, the hydraulic oil inside the hydraulic actuator cylinder 12 decreases, generating tension, and the auxiliary main rod 9 continues to rotate downwards, ultimately achieving the complete lowering of the landing gear (as shown). Figure 10(As shown); During this process, the nose landing gear door 5 is opened by the control system before the landing gear is lowered, and remains open after the landing gear is fully lowered to ensure that the landing gear and door do not interfere with each other and to ensure smooth system operation. It should be noted that when the landing gear is lowered, the hydraulic connecting rod 11 works first. After the hydraulic connecting rod 11 completes the lowering process, the hydraulic actuator rod 12 will start to work until the landing gear is fully lowered.

[0039] In terms of auxiliary functions, the steering mechanism 8 is sleeved on the main rod 9 via a steering sleeve 81, and can rotate around the main rod 9 (range -45° to 45°), driving the wheels 7 and hydraulic shock absorbers 10 to turn synchronously, achieving precise directional adjustment during ground gliding. Simultaneously, the steering gear 83 meshes with the power gear 172 of the steering drive device 17, transmitting the torque output from the steering motor 171 to the steering sleeve 81, thereby adjusting the direction. For example, the wheels 7 turn 45° to the left. Figure 7 As shown, turn 45° to the right. Figure 8 As shown; the hydraulic shock absorber 10 is placed inside the main rod 9. It converts the landing impact kinetic energy into internal energy by squeezing hydraulic oil, effectively absorbing the ground load and allowing it to rotate around the main rod 9, significantly improving the shock absorption performance; the wheel 7 adopts a non-powered design to reduce the overall weight. It is driven to rotate by the aircraft thrust during taxiing, and absorbs the impact through the friction between the rubber material and the runway during landing, providing direct and efficient shock absorption support for the aircraft.

[0040] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A military attack unmanned aerial vehicle front landing gear retraction system characterized in that, The front fuselage (1) includes a fuselage frame (4) and a fuselage skin (3), the front landing gear support shaft (6) is fixed on the fuselage frame (4) through a combination structure of a polygonal end face and a nut, and the bottom of the front fuselage (1) is rotatably provided with two front landing gear doors (5) and a control mechanism for driving the front landing gear doors (5) to open and close. The front landing gear (2) includes a wheel (7), a steering mechanism (8), a main rod (9), a hydraulic shock cylinder (10), a front fork (16) and a driving mechanism for driving the main rod (9) to rotate, wherein the steering mechanism (8) includes a steering sleeve (81), a steering knuckle arm (82), a steering gear (83) and a steering driving device (17). The main rod (9) is provided with a slanted arm (91) on each side of the upper end, and the end of the slanted arm (91) is provided with a mounting cylinder (92) which is sleeved with the front landing gear support shaft (6) through a fixed bearing, and the front landing gear (2) can rotate around the front landing gear support shaft (6) under the action of the rotating torque provided by the driving mechanism. The front fork (16) is provided with the wheel (7), and the upper end of the front fork (16) is provided with two groups of fork arms, i.e. a first group of fork arms (161) and a second group of fork arms (162), wherein the second group of fork arms (162) is a movable fork arm. The lower end of the main rod (9) is rotatably provided with the hydraulic shock cylinder (10) through a bearing, the lower connecting end of the hydraulic shock cylinder (10) is rotatably connected with the second group of fork arms (162), the first group of fork arms (161) is rotatably connected with the lower end of the steering knuckle arm (82), the upper end of the steering knuckle arm (82) is provided with the steering sleeve (81) with the outer circumferential wall with the steering gear (83), and the steering sleeve (81) is sleeved with the main rod (9) through a bearing. The steering driving device (17) includes a steering motor (171) which is fixedly installed on the main rod (9), and the output end of the steering motor (171) is provided with a power gear (172) which is engaged with the steering gear (83). The driving mechanism includes a hydraulic connecting rod (11), a hydraulic actuator cylinder (12) and a support seat rod (13). The support seat rod (13) includes a first herringbone rod (131), and the intersection end of the first herringbone rod (131) is fixed on the fuselage frame (4) and is provided with a threaded cylinder (1311). The bifurcated end of the first herringbone rod (131) is provided with a mounting hole (133) which is sleeved with the front landing gear support shaft (6) through a bearing. The bifurcated end of the first herringbone rod (131) extends upward and intersects again to form a second herringbone rod (132), and the intersection of the second herringbone rod (132) is provided with a positioning cylinder (1321), the cylinder body of the hydraulic actuator cylinder (12) is axially positioned by the positioning cylinder (1321), the shell end is fixedly assembled with the threaded cylinder (1311) through threads, the output end of the hydraulic actuator cylinder (12) is hingedly connected with one end of the hydraulic connecting rod (11), and the other end of the hydraulic connecting rod (11) is hingedly connected with the main rod (9). ​ 2. A military attack UAV front landing gear retraction system according to claim 1, characterized in that, The threaded hole (1312) is arranged in the threaded cylinder (1311), and the positioning hole (1322) is arranged in the positioning cylinder (1321), the cylinder body of the hydraulic operating cylinder (12) passes through the positioning hole (1322), and the shell end is fixedly connected with the threaded hole (1312) through screw threads.

3. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The first herringbone-shaped rod (131) and the second herringbone-shaped rod (132) are both provided with a hollow structure.

4. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The inner ring of the fixed bearing is in interference fit with the front landing gear support shaft (6), and the outer ring of the fixed bearing is in interference fit with the mounting hole of the mounting cylinder (92).

5. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The fixed bearing is a deep groove ball bearing, and the dust covers on both sides of the fixed bearing are tightly attached to the inner walls of the mounting hole of the mounting cylinder (92).

6. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The polygonal end face is a regular hexagonal structure, and the fuselage frame (4) is provided with a hexagonal mounting groove matched with the regular hexagonal end face.

7. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The control mechanism comprises a double-acting hydraulic rod (51), two ends of the two front landing gear doors (5) are connected with the fuselage frame (4) through front hinges (52) and rear hinges (53), the front hinges (52) and the rear hinges (53) both comprise a base (531), a hinge shaft (532) and an arc-shaped connecting piece (533), the base (531) is installed on the fuselage frame (4), one end of the arc-shaped connecting piece (533) is hinged to the base (531) through the hinge shaft (532), and the other end is fixedly connected with the inner surface of the front landing gear door (5); The front hinge (52) further comprises a connecting plate (534) arranged on the arc-shaped connecting piece (533), one end of the double-acting hydraulic rod (51) is installed on the fuselage frame (4) through a hinge seat, and the other end is hinged to the connecting plate (534); When the double-acting hydraulic rod (51) works, the arc-shaped connecting piece (533) is driven to rotate around the hinge shaft (532) through the connecting plate (534), so that the front landing gear door (5) is driven to realize the opening and closing action of a preset angle.

8. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The rotation angle range of the front landing gear (2) around the front landing gear support shaft (6) is 0°-77°, 0° corresponds to the laid-down state of the front landing gear (2), and 77° corresponds to the stowed state of the front landing gear (2).

9. The military attack UAV front landing gear retraction system according to claim 1, characterized in that, The abutting surface of the front landing gear door (5) and the fuselage skin (3) is provided with a rubber sealing element (54), and the edge of the front landing gear door (5) is provided with a groove for accommodating the rubber sealing element.

10. The military attack UAV front landing gear retraction system according to claim 7, characterized in that, The front hinge (52) and the rear hinge (53) are both made of stainless steel.

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