A three-stage retractable rocker-type landing gear

Abstract

A three-stage retractable rocker-type landing gear. The upper end of the diagonal truss beam is hinged to the front landing gear fixing frame located in the landing gear bay of the aircraft through a front pin bolt. The lower end is hinged to the lower end of the vertical U-shaped strut through a pin shaft with a pull hole, enabling the double-ended lever to rotate around the double-ended lever fulcrum shaft. A double-ended lever is installed at the upper end of the diagonal truss beam. The rotary cross beam of the rocker is sleeved on the pin shaft with a pull hole; the lower end of the vertical U-shaped strut is also sleeved at both ends on the pin shaft with a pull hole in a hinged manner. The two ends of the double-ended lever are respectively hinged to the main buffer and the rocker lug. By cooperating with the double-ended lever and the actuator installed at one end of the buffer, the present invention obtains an additional retraction and extension stroke while having the same buffering function as a conventional landing gear, realizes a retraction and extension with higher space utilization rate, reduces the requirement for the landing gear bay space, reduces the horizontal bulkiness of the landing gear bay, and meets better requirements for the aerodynamic shape of the aircraft. The retraction actuation can be carried out simultaneously.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and specifically to a rocker-type landing gear that can be retracted in three stages. Background Art

[0002] The aircraft landing gear is the only load-bearing component of the aircraft on the ground. Its main function is to support the aircraft load during the takeoff, taxiing, landing, and parking processes of the aircraft. For the components of the landing gear itself, it mainly consists of connecting rods, shock absorbers, and wheels. The load-bearing members are rigid components that cannot be folded or compressed. The shock absorbers are connected by hinges, and the shock absorbers are connected to the wheel brackets. The shock absorbers and wheels function as buffers during the aircraft landing process, absorbing most of the ground impact energy. For modern aircraft, in order to obtain excellent high-speed performance, the outer shape is almost a perfect streamline. When the landing gear is not involved in sharing the aircraft load during flight, it needs to be retracted into the landing gear compartment. For a transport aircraft, in order to occupy as little space in the aircraft cabin as possible, a transport aircraft generally designs a separate bulge on the outside of the fuselage to serve as the landing gear retraction compartment. The most direct factor affecting the size of the landing gear compartment bulge is the space size after the landing gear is retracted.

[0003] After retrieval, the technical solutions adopted by the landing gears in the prior art are as follows:

[0004] A utility model patent with the authorization announcement number CN214824065U discloses an aircraft landing gear retraction device. The device includes a storage cavity. The top of the right side wall of the storage cavity is rotatably connected to a rotating plate. A main bracket is rotatably connected to the rotating plate. A wheel set is arranged at the end of the main bracket. A side bracket is hinged to the main bracket. One end of the side bracket away from the main bracket is slidably connected to the rotating plate. A first electric push rod is fixedly connected to the rotating plate. The end of the telescopic rod of the first electric push rod is connected to one end of the side bracket away from the main bracket. A second electric push rod is hinged to the top of the storage cavity. The end of the telescopic rod of the second electric push rod is hinged to the main bracket. The structure of the present utility model is simple, effectively reducing the space occupied by the landing gear when retracted. However, this landing gear retraction device does not consider the impact force transmission path of large heavy-duty aircraft. From the disclosed structure, its side bracket is the main aircraft body load-bearing component, which is not suitable for actual engineering aircraft. Although it does consider the space utilization rate of the landing gear compartment after retraction, it compromises the rationality of the structural layout.

[0005] A retractable nose landing gear mechanism for a light sport aircraft is disclosed in the utility model with the authorization announcement number CN211076320U. The retractable nose landing gear mechanism includes a fuselage assembly. The fuselage assembly is rotatably connected with a landing gear rod through a mounting joint. The bottom of the landing gear rod is fixedly connected with a nose landing gear wheel through a pivot. In this utility model, when the handle is shaken, the rotating shaft rotates, and the worm is driven to rotate through the transmission shaft and the universal joint. The worm drives the worm wheel to rotate. The worm wheel drives the rocker arm integrally welded to its outer wall to swing. While the rocker arm drives the shock absorption assembly to move linearly, the landing gear rod rotates around the mounting joint, the landing gear retracts upward, and the wheel set is received into the fuselage assembly. The operation of lowering the landing gear is opposite to the above operation, and the wheel set is limited when retracting and lowering through a stop member, thereby realizing the retraction and extension of the nose landing gear and improving the use effect of the retractable nose landing gear mechanism. The disclosed retractable nose landing gear mechanism uses a worm and worm gear for transmission, which is a novel form of landing gear retraction and extension. However, the power device and transmission components occupy a large amount of cabin space.

[0006] An aircraft landing gear retractable device is disclosed in the utility model patent with the authorization announcement number CN203876981U. The device includes a landing gear composed of a tire and a frame. The landing gear is connected to a retractable device. The retractable device includes a connecting rod with one end connected to the frame. The other end of the connecting rod is connected to one end of a push rod. The other end of the push rod is connected to a hydraulic output rod through a second connector. The hydraulic output rod is connected to a hydraulic cylinder. Among them, the second connector includes a locking device arranged at the end of the push rod. The locking device cooperates with a lock catch at the end of the hydraulic output rod. A connecting buckle is arranged on the locking device. In this utility model, the landing gear is separated and lowered manually. The operation steps are simple, convenient and fast. It only takes a few minutes to lower the landing gear, and it can be completed within one minute at the fastest, greatly improving the safety of the aircraft in case of emergency, and having a wide range of applications. However, the disclosed mechanism only shows theoretical schematic components, and does not explain the position and occupied space of the retracted landing gear.

[0007] An aircraft main landing gear spatial retractable mechanism and retractable method are disclosed in the invention patent with the announcement number CN102431644B. This patent belongs to the field of aircraft landing gear design. In order to solve the problems that the existing landing gear needs to be flipped and the landing gear door retractable mechanism and control system are complex, the invention is composed of a five-bar and five-pair spatial retractable mechanism and a planar four-bar linkage driving mechanism. Among them, the five-bar and five-pair spatial retractable mechanism is composed of a cross beam, a pivot, an outer cylinder, a rocker arm and a rotating sleeve. The combined planar four-bar linkage driving mechanism is composed of a connecting rod assembly, a lever, a bracket and a driving actuator retractable cylinder. The invention realizes the spatial retraction and extension of the landing gear by using kinematic pairs such as universal joints and rotations, and simplifies the design of the landing gear door and retractable control system.

[0008] The disclosed space retractable mechanism simplifies the landing gear door. It has a certain spatial angle through the connecting shaft between the landing gear and the fuselage, enabling the entire landing gear to rotate around it to retract the wheel shaft spatially backward, which is a first-level retraction process.

[0009] In the invention disclosed in US2020 / 0398974A1, a SEMI-LEVERED SHRINK LANDING GEAR for an aircraft is disclosed. The landing gear includes a shock absorber strut and an anti-rotation link. The shock absorber strut is at least partially located inside the aircraft and is guided in its movement by a guiding member connected to the aircraft frame. The shock absorber strut includes an outer cylinder, which is shaped and sized to engage the guiding member, wherein the guiding member guides the sliding movement of the outer cylinder, and the outer cylinder is configured to be driven in a sliding movement relative to the guiding member, and an inner cylinder disposed at least partially inside the outer cylinder. The anti-rotation link includes a connecting plate connected to the outer cylinder of the shock absorber strut, and an anti-rotation link assembly coupled to both the guiding member and the connecting plate, and the anti-rotation link assembly is configured to hold the shock absorber strut in a fixed rotational direction relative to the guiding member.

[0010] The landing gear system of an aircraft disclosed in US202163229043P includes a drag support, a lateral support, and a support assembly. The support assembly is coupled to the side of the fuselage through a side bracket, the upper part of the fuselage through a hinge, and the front of the fuselage through a drag bracket. The support assembly can rotate around the hinge connection around the front-rear axis. The lateral support of the support assembly resists rotation around the front-rear axis, and the drag support of the support assembly resists rotation around the vertical axis. The system includes an inboard landing gear and an outboard landing gear, which are respectively connected to the support assembly to support the weight of the aircraft. The hinge transfers the vertical force to the fuselage, the moment around the hinge is reacted by the force on the side strut, and the drag is transferred to the fuselage through the drag bracket. This invention discloses a landing gear system with a multi-wheel group rocker arm structure, considering the force transmission path and load in actual engineering applications. However, the size of this landing gear is very large, and the retraction is simply lifting, so the landing gear bay space needs to be designed very large, occupying too much internal space of the cabin or having a huge landing gear bay bulge.

[0011] AIRCRAFT LANDING GEAR is disclosed in CA2972157A1. The aircraft landing gear has a shock absorber strut and a shortening mechanism coupled between a walking beam and a shortened portion of the shock absorber. The shortening mechanism is arranged such that when the walking beam is in a first position due to a first extended state of a retraction actuator, the shortening mechanism is in a locked state, in which it inhibits axial movement of the shortened portion within the strut element in a first direction axial direction, and when the retraction actuator changes from the first extended state to a second extended state in an extended state, the retraction actuator moves the walking beam, thereby causing the shortening mechanism to axially move the shortened portion within the strut element in a first axial direction to shorten the shock absorber strut. The disclosed landing gear realizes the retraction function by directly acting on the buffer strut through a retraction and extension actuator, and the strut mechanism maintains stability and realizes the locking function. The landing gear realizes retraction and extension with one degree of freedom in space.

[0012] In the IRCRAFT LANDING GEAR ASSEMBLY disclosed in EP3868656A1, the landing gear is an aircraft landing gear assembly, including: a structural pin defining a first hole having a longitudinal insertion axis (IA); a cover for covering the hole, the cover including: a base portion, a head portion, a body portion located between the base portion and the head portion; and a bolt extending between the head portion and the base portion and including a threaded portion such that engagement of the head portion or the base portion with the threaded portion causes the head portion or the base portion to move relative to the other, the body being made of an elastically deformable material such that when the bolt is tightened, the base portion moves towards the head portion and the elastically deformable material moves radially outwards such that the contact surface of the elastically deformable material engages the inner surface of the first hole to retain the cover. The disclosed landing gear realizes the retraction function by directly acting on the buffer strut through a retraction and extension actuator, and the strut mechanism maintains stability and realizes the locking function. The landing gear realizes side retraction, that is, retraction and extension with one degree of freedom in space, and is a simple first-stage retraction and extension. SUMMARY OF THE INVENTION

[0013] To overcome the deficiency of low utilization rate of the landing gear bay in the prior art, the present invention proposes a rocker-type landing gear that can be retracted and extended in three stages.

[0014] The present invention includes a side retractable actuator, a wheel, a vertical U-shaped strut, a main buffer, a diagonal girder, a double-ended lever, a front landing gear fixing bracket, a rocker arm, a pin shaft with a pulling hole, a rear landing gear fixing member, a side retractable actuator fuselage fixing member, and a driving member; the driving member includes a side retractable actuator and a double-ended lever actuator. Among them, the upper end of the diagonal girder is hinged to the front landing gear fixing bracket located in the landing gear compartment of the aircraft through a front pin bolt, and the lower end is hinged to the lower end of the vertical U-shaped strut through a pin shaft with a pulling hole, enabling the double-ended lever to rotate around the double-ended lever fulcrum shaft. The center line of the front pin bolt is coaxial with the center line of the hinge shaft of the vertical U-shaped strut and the fuselage fixing member and parallel to the course.

[0015] A double-ended lever is installed at the upper end of the diagonal girder. The center line of the double-ended lever fulcrum shaft for installing the double-ended lever is parallel to the center line of the pin shaft with a pulling hole and perpendicular to the course.

[0016] The rotary cross beam at the lower end of the rocker arm is sleeved on the pin shaft with a pulling hole, enabling the rocker arm to rotate around the pin shaft with a pulling hole; the lower end of the vertical U-shaped strut is also sleeved on the pin shaft with a pulling hole and located at both ends of the pin shaft with a pulling hole.

[0017] One end of the double-ended lever is hinged to the main buffer; the other end of the main buffer is hinged to the upper end of the rocker arm lug. The lower end of the rocker arm lug is connected to the rocker arm. The side retractable actuator is located on one side of the main buffer. The upper end of the vertical U-shaped strut is hinged to the rear landing gear fixing member located in the landing gear compartment of the aircraft.

[0018] The vertical U-shaped strut includes an inner U-shaped frame, an outer U-shaped frame, and a plurality of support rods. There is a through hole for connecting to the rear landing gear fixing member at the top of the arc-shaped rod of the outer U-shaped frame; a plurality of support rods are provided between the outer arc surface of the inner U-shaped frame and the inner arc surface of the outer U-shaped frame. The two side plates at the open end of the inner U-shaped frame are respectively connected to the two side plates at the open end of the corresponding side of the outer U-shaped frame. There are through holes for connecting to the diagonal girder on the two side plates at the U-shaped open end of the vertical U-shaped strut. The distance between the two side plates of the vertical U-shaped strut meets the connection requirements of the large end of the diagonal girder.

[0019] There are installation holes for a diagonal girder pin bolt and a double-ended lever fulcrum shaft at the small end of the diagonal girder, and a connection hole for the vertical U-shaped strut at the large end of the diagonal girder. The inner width of the diagonal girder meets the installation requirements of the main buffer.

[0020] There is a through hole for hinging at the intersection of the angle bisectors of the double-ended lever. The two bottom corners of the double-ended lever respectively have U-shaped grooves, and each U-shaped groove penetrates the surfaces of the two hypotenuses and the bottom edge of the double-ended lever; there are coaxial through holes on both side walls of the U-shaped groove.

[0021] One end of the side retractable actuator rod is hinged to the fixed part on the fuselage, and the other end is connected to the diagonal truss beam through a pin shaft with a pulling hole.

[0022] The retraction and extension process of the three-stage rocker-type landing gear is as follows:

[0023] The first-stage retraction process of the landing gear: The aircraft oil pump works, and the oil in the squatting cavity of the main buffer is discharged, realizing the contraction of the inner cylinder, and pulling the rocker to rotate around the rear pin shaft by a certain angle. The retraction in this process is a large-scale retraction. When the landing gear is retracted and extended, the main buffer is used as an actuator, that is, the squatting cavity is enabled. The main buffer contracts and locks in the upper position / retracted position, pulling the rocker and the wheel upward;

[0024] The second-stage retraction process of the landing gear: When the main buffer contracts and locks in the upper position, the double-ended lever actuator generates a pulling force on one end of the long arm of the double-ended lever. At this time, an upward pulling force is generated at one end of the short arm where the double-ended lever is hinged to the outer cylinder of the main buffer. At this time, the main buffer can be regarded as a transmission part, and the rocker at the other end of the main buffer is pulled to rotate around the pin shaft with a pulling hole by a certain angle. The second-stage retraction action is completed.

[0025] The third-stage retraction process of the landing gear: The side retractable actuator is activated to generate a pulling force, which acts on the end hole of the pin shaft with a pulling hole, driving the entire landing gear to rotate around the heading by a certain angle and being stored in the landing gear compartment to complete the third-stage retraction action. The lowering process is the opposite working condition.

[0026] The present invention proposes a brand-new, efficient, and compact retractable rocker-type landing gear, which has the characteristics of simple and efficient form structure, low requirements for the space of the landing gear compartment, and high reliability. Moreover, the structure of this landing gear also takes into account the large impact load during aircraft landing and has considerable future research prospects.

[0027] The present invention mainly cooperates the double-ended lever and the actuator installed at one end of the buffer. While having the same buffer function as the conventional landing gear, it obtains an additional retraction and extension stroke, realizes a higher space utilization rate for retraction and extension, reduces the requirements for the space of the landing gear compartment, reduces the horizontal bulkiness of the landing gear compartment, and meets the better aerodynamic shape requirements of the aircraft. The retraction actuation can be carried out simultaneously.

[0028] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0029] 1. By installing a double-ended lever on the diagonal truss beam through a through hole to connect the main buffer, it not only maintains the excellent buffer performance and reasonable force transmission path of the rocker type, but also can further lift the landing gear wheel axle through the rotation of the double-ended lever. The retracted posture of the landing gear is more compact, obtaining an additional retraction stroke, and the external bulge design of the landing gear compartment can also be made smaller.

[0030] 2. By designing the vertical U-shaped strut and the pin shaft at the front end of the diagonal girder beam to be on the same axis as the hinge axis of the airframe, the landing gear that could originally only be lifted up and down can be further retracted laterally, making the retracted position of the landing gear closer to the airframe. With the goal of occupying as little internal space of the cabin as possible, the landing gear bay can be designed to be more compact, with higher space utilization rate, smaller cross-sectional area of the aircraft, and better aerodynamic shape.

[0031] 3. The design of this landing gear incorporates a double-chamber buffer, with both a buffer chamber and a squat chamber. After the aircraft squats on the ground, the bottom plate of the cargo hold can be lowered, and then loading and unloading can be carried out, improving the efficiency of loading and unloading goods. Generally speaking, it is a multi-functional landing gear with good retraction and extension performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a three-dimensional structure schematic diagram of the present invention, and the arrow in the figure indicates the course line.

[0033] Figure 2 is Figure 1 the front view in the course direction.

[0034] Figure 3 It is a structure schematic diagram of the diagonal girder beam; among them, Figure 3 a is the front view, Figure 3 b is Figure 3 the left view of a, Figure 3 c is Figure 3 the sectional view taken along the C-C direction in a.

[0035] Figure 4 It is a structure schematic diagram of the pin shaft with a pulling hole; among them, Figure 4 a is the sectional view of the main axis, Figure 4 b is the three-dimensional structure diagram.

[0036] Figure 5 It is a structure schematic diagram of the double-end lever; among them, Figure 5 a is the side view, Figure 5 b is the front view, Figure 5 c is the isometric view of the second angle, Figure 5 d is the top view.

[0037] Figure 6 It is a structure schematic diagram of the rocker arm; among them, Figure 6 a is the front view, Figure 6 b is the side view, Figure 6 c is the top view, Figure 6 d is the axonometric view.

[0038] Figure 7 It is a structure schematic diagram of the front fixed frame of the landing gear; among them, Figure 7 a is the front view, Figure 7b is the rear side axonometric view.

[0039] Figure 8 It is a schematic diagram of the first stage of the landing gear retraction of the present invention; wherein, Figure 8 a is the position before the first stage of retraction, Figure 8 b is the position after the first stage of retraction.

[0040] Figure 9 It is a schematic diagram of the second stage of the landing gear retraction of the present invention; wherein, Figure 9 a is the position before the second stage of retraction, Figure 9 b is the position during the second stage of retraction, Figure 9 c is the position after the second stage of retraction is completed.

[0041] Figure 10 It is a schematic diagram of the third stage of the landing gear retraction of the present invention; wherein, Figure 10 a of the third stage is the position before retraction, Figure 10 b is Figure 10 a partial enlarged view of part A in a, Figure 10 c is the position after the third stage of retraction is completed.

[0042] Figure 11 It is the spatial position of each component of the landing gear of the present invention when the aircraft is about to land.

[0043] Figure 12 It is an explanatory diagram of the dead point position of the crank-rocker mechanism; in the figure: A is the simplified rod diagram of the double-end lever, B is the simplified rod diagram of the main buffer, and C is the schematic diagram of the position of the rocker arm.

[0044] Figure 13 It is an explanatory diagram of the technical solution of the retraction process of the present invention.

[0045] Figure 14 It is a schematic diagram of the structure of the landing gear retraction device of the aircraft proposed in CN214824065U.

[0046] Figure 15 It is a schematic diagram of the structure of a retraction mechanism for the nose landing gear of a light sport aircraft proposed in CN211076320U.

[0047] Figure 16 It is a schematic diagram of the structure of the landing gear retraction device of the aircraft disclosed in CN203876981U.

[0048] Figure 17 It is a schematic diagram of the structure of the retraction mechanism in the spatial retraction mechanism and retraction method of the main landing gear of the aircraft proposed in CN102431644B; wherein, a is the rear view, b is the front view, and c is the axonometric view.

[0049] Figure 18It is a schematic structural diagram of the landing gear of an aircraft proposed in US2020 / 0398974A1.

[0050] Figure 19 It is a schematic structural diagram of the landing gear system of an aircraft proposed in US202163229043P.

[0051] Figure 20 It is a schematic structural diagram of the landing gear of an aircraft proposed in CA2972157A1, where a is the state of the landing gear being lowered and extended, and b is the state of the landing gear being retracted.

[0052] Figure 21 It is a schematic composition diagram of the landing gear assembly proposed in EP3868656A11.

[0053] In the figure: 1. fuselage; 2. side retraction and extension actuator; 3. wheel; 4. vertical U-shaped strut; 5. main buffer; 6. diagonal truss beam; 7. double-ended lever actuator; 8. double-ended lever; 9. front landing gear fixing bracket; 10. rocker arm; 11. pin shaft with a pulling hole; 12. rocker arm lug; 13. rear landing gear fixing part; 14. side retraction and extension actuator fuselage fixing part; 15. diagonal truss beam bolt; 16. double-ended lever fulcrum shaft; 17. hinge shaft between the double-ended lever actuator and the double-ended lever; 18. landing gear bay. Specific implementation mode

[0054] This embodiment is a rocker-type landing gear that can be retracted in three stages, including a side retraction and extension actuator 2, a wheel 3, a vertical U-shaped strut 4, a main buffer 5, a diagonal truss beam 6, a double-ended lever 8, a front landing gear fixing bracket 9, a rocker arm 10, a pin shaft with a pulling hole 11, a rear landing gear fixing part 13, a side retraction and extension actuator fuselage fixing part 14, and a driving part. The driving part includes a side retraction and extension actuator 2 and a double-ended lever actuator 7. Among them, the upper end of the diagonal truss beam 6 is hinged to the front landing gear fixing bracket 9 located in the landing gear bay 18 of the aircraft through a front-end bolt 15, and the lower end is hinged to the lower end of the vertical U-shaped strut 4 through a pin shaft with a pulling hole 11, so that the double-ended lever 8 can rotate around the double-ended lever fulcrum shaft 16. The center line of the front-end bolt 15 and the center line of the hinge shaft between the vertical U-shaped strut 4 and the fuselage fixing part 13 are coaxial and parallel to the heading.

[0055] A double-ended lever 8 is installed at the upper end of the diagonal truss beam. The center line of the double-ended lever fulcrum shaft 16 for installing the double-ended lever is parallel to the center line of the pin shaft with a pulling hole 11 and perpendicular to the heading.

[0056] The rotary cross beam at the lower end of the rocker arm 10 is sleeved on the pin shaft with a pulling hole, so that the rocker arm 10 can rotate around the pin shaft with a pulling hole 11; the lower end of the vertical U-shaped strut 4 is also sleeved on the pin shaft with a pulling hole and is located at both ends of the pin shaft with a pulling hole.

[0057] The double-ended lever is hinged to one end of the main buffer 5; the other end of the main buffer is hinged to the upper end of the rocker lug 12. The lower end of the rocker lug is connected to the rocker arm 10. The side retracting and extending actuator 2 is located on one side of the main buffer. The upper end of the vertical U-shaped strut 4 is hinged to the rear landing gear fixing member 13 located in the landing gear bay 18 of the aircraft.

[0058] The connection of the diagonal girder 6, the vertical U-shaped strut 4 and the fuselage 1 forms a stable triangular support, and this triangular support is the main body of the entire landing gear structure.

[0059] The side retracting and extending actuator 2 adopts the existing technology.

[0060] The vertical U-shaped strut 4 is U-shaped in appearance and includes an inner U-shaped frame, an outer U-shaped frame and a plurality of support rods. There is a through hole for connecting to the rear landing gear fixing member 13 at the top of the arc-shaped rod of the outer U-shaped frame; a plurality of support rods are provided between the outer arc surface of the inner U-shaped frame and the inner arc surface of the outer U-shaped frame. The two side plates at the open end of the inner U-shaped frame are respectively connected to the two side plates at the open end of the outer U-shaped frame on the corresponding side. There are through holes for connecting to the diagonal girder 6 on the two side plates at the U-shaped open end of the vertical U-shaped strut 4. The distance between the two side plates of the vertical U-shaped strut meets the connection requirements of the large end of the diagonal girder.

[0061] The diagonal girder 6 is a rod member and is isosceles trapezoidal in appearance. There are mounting holes for the diagonal girder bolt and the fulcrum shaft 16 of the double-ended lever at the small end of the diagonal girder, and a connection hole for the vertical U-shaped strut 4 at the large end of the diagonal girder. The inner width of the diagonal girder meets the installation of the main buffer 5.

[0062] The double-ended lever 8 is block-shaped and is isosceles triangular in appearance. There is a through hole for hinging at the incenter of the double-ended lever, that is, the intersection of the angle bisectors of the double-ended lever. The two base angles of the double-ended lever respectively have U-shaped grooves, and each U-shaped groove penetrates the surfaces of the two hypotenuses and the base of the double-ended lever; there are coaxial through holes on both side walls of the U-shaped groove.

[0063] The side retracting and extending actuator fuselage fixing member 14 is concave-shaped; there are hinging holes for the side retracting and extending actuator 2 on the two side walls of the side retracting and extending actuator fuselage fixing member.

[0064] One end of the rocker lug 12 is fixedly connected to the outer surface of the rocker arm sleeve 10; the other end of the rocker lug is hinged to the main buffer 5.

[0065] Specifically, the front fuselage fixing frame 9 plays the role of fixing the diagonal girder 6, that is, it bears a part of the aircraft fuselage load. The front fuselage fixing frame 9 is a space tripod. The bottom edge of the triangular fixing surface is attached to the fuselage and fixed thereto, and the other side is perpendicular to the axis of the fuselage 1, and a bearing is assembled between the positioning hole of the front fixing member 15 and the diagonal girder 6, releasing the freedom of the landing gear to rotate around the heading direction and eliminating the heading displacement generated during landing.

[0066] The rear fuselage fixing member 13 serves to fix the vertical U-shaped strut 4 and bear the main fuselage load of the landing gear. In this example, the vertical U-shaped strut 4 and the rear fuselage 1 landing gear fixing member 13 are also assembled with bearings. The rear fuselage fixing member 13 is a double-ear structure fixed on the fuselage structure to provide the landing gear with freedom to rotate around the heading direction.

[0067] In this embodiment, the oblique truss 6 is in an isosceles trapezoidal shape as a whole, with an I-shaped cross section and a side profile in a factory shape. There is an ear structure for connecting the double-end lever actuator 7 at the center of the web on the bottom side. The vertical U-shaped support 4 is in an inverted U shape as a whole, with an ear through hole for assembling on the rear fixing member 13 of the aircraft fuselage landing gear at the upper end, and a pin hole at the lower two end support plate structures. The double-end lever 8 is an asymmetric structure at its middle hole axis. The structural feature is that one end of the beam arm of the hinged double-end lever actuator 7 is longer than the end of the hinged main buffer 5, and there is a groove for weight reduction and material removal. The present invention does not make special requirements and explanations for the groove. The material removal groove can be reasonably designed while ensuring strong rigidity in the subsequent design, so that the double-end lever actuator 7 has lower requirements on strength and the push-pull force that can be provided, so that the structural size of the double-end lever actuator 7 is maintained at a smaller level.

[0068] One end of the side retracting actuator 2 rod is hinged to the fixing part 14 on the fuselage, and the other end is connected to the diagonal girder 6 through the pin shaft 11 with a pulling hole. When the aircraft oil pump works, it delivers pressure oil to the side retracting actuator 2 or extracts oil, generating thrust or pulling force and acting on the pulling hole of the pin shaft 11 with a pulling hole on the inner side close to the fuselage. Since the pin shaft 11 hinges the diagonal girder 6, the rocker arm 10 and the vertical U-shaped support 4 in series, the entire landing gear generates a driving force to rotate around the heading direction, so that the landing gear can be stored in the landing gear compartment, so as to further save cabin space and obtain a smoother aerodynamic shape. When it is released from the landing gear compartment during landing, the working situation is opposite.

[0069] When the aircraft lands, the landing gear has to withstand the impact landing load. Therefore, it is specifically stated that when landing, the hinge point of the double-ended lever 8 with the main buffer 5, the axis of the fulcrum shaft 16 of the double-ended lever, and the axis of the hinge point of the lug 12 with the main buffer 5 are on the same straight line, forming a mechanical dead center. In this way, it is not necessary for the double-ended lever actuator 7 to bear a huge load, and only the load for assisting the double-ended lever 8 needs to be provided. During the landing process, the retraction and extension function of the main buffer 5 is turned off and the retraction and extension action cannot be performed. Explanation: In a planar linkage mechanism, if the rocker or slider is used as the driving member, when the other two moving members are in the position of being on the same straight line, no matter how large the driving force is, the mechanism cannot be started. For example, in a crank-rocker mechanism, when the rocker is the driving member and the crank is in the two extreme positions where it is in a straight line with the connecting rod, the force transmitted by the connecting rod to the crank cannot generate a torque to make the crank rotate.

[0070] In this embodiment, the main buffer 5 is a double-chamber buffer with a buffer chamber and a squatting chamber. By filling or discharging oil in the squatting chamber, the elongation / retraction of the buffer can be achieved, which is a prior art and is not protected or claimed in the present invention.

[0071] The working principle of the three-stage rocker-type landing gear retraction mechanism is as follows:

[0072] The first-stage retraction process of the landing gear of the present invention is as Figure 8 shown. The aircraft oil pump works, and the oil in the squatting chamber of the main buffer 5 is discharged, realizing the contraction of the inner cylinder and pulling the rocker arm 10 to rotate around the rear pin shaft 11 by a certain angle. The retraction in this process is a large-scale retraction. When the landing gear is retracted and extended, the main buffer 5 is used as an actuator, that is, the squatting chamber is enabled. The main buffer 5 contracts and is locked in the upper position / retracted position, pulling the rocker arm 10 and the wheel 3 upward for retraction;

[0073] The second-stage retraction process of the landing gear of the present invention is as Figure 9 shown. When the main buffer 5 contracts and is locked in the upper position, the double-ended lever actuator 7 generates a pulling force on one end of the long arm of the double-ended lever 8. At this time, an upward pulling force is generated at one end of the short arm of the double-ended lever 8 hinged to the outer cylinder of the main buffer 5. At this time, the main buffer can be regarded as a transmission member, and the other end of the main buffer pulls the rocker arm 10 to rotate around the pin shaft 11 with a pulling hole by a certain angle. The secondary retraction action is completed.

[0074] Preferably, in the present invention, when the landing gear wheel is further retracted upward in this way, an additional retraction space stroke can be obtained. This additional stroke is as Figure 7 schematic. Δh = h0 - h1 can reduce the longitudinal dimension of the aircraft landing gear compartment protruding from the bottom side of the fuselage to a certain extent.

[0075] The third-stage retraction process of the landing gear of the present invention is as Figure 10As shown, the side retraction and extension actuator 2 starts to generate a pulling force, which acts on the end hole of the pin shaft 11 with a pulling hole, driving the entire landing gear to rotate by a certain angle around the heading, and being stored in the landing gear compartment to complete the three-stage retraction action. The working condition during the lowering process is the opposite. Preferably, after the landing gear is internally combined in this way, the horizontal width of the landing gear compartment protruding outside the fuselage can be reduced by a certain dimension ΔS = S0 - S1.

[0076] The overall retraction action process of the present invention is shown in Figure 13 As shown, the principle of lowering the landing gear is the same, but the actions are opposite.

Claims

1. A rocker-type landing gear capable of three-stage retraction and extension, characterized in that It includes a side retraction and extension actuator, a wheel, a vertical U-shaped strut, a main buffer, a diagonal girder, a double-ended lever, a front landing gear fixing bracket, a rocker arm, a pin with a hole for pulling, a rear landing gear fixing part, a side retraction and extension actuator fuselage fixing part and a driving part; the driving part includes a side retraction and extension actuator and a double-ended lever actuator; wherein, the upper end of the diagonal girder is hinged to the front landing gear fixing bracket located in the landing gear compartment of the aircraft through a front pin, and the lower end is hinged to the lower end of the vertical U-shaped strut through a pin with a hole for pulling, enabling the double-ended lever to rotate around the double-ended lever fulcrum axis; the center line of the front pin and the center line of the hinge axis of the vertical U-shaped strut and the fuselage fixing part are coaxial and parallel to the course; A double-ended lever is installed at the upper end of the diagonal girder; the center line of the double-ended lever fulcrum axis for installing the double-ended lever is parallel to the center line of the pin with a hole for pulling and perpendicular to the course; The rotary cross beam at the lower end of the rocker arm is sleeved on the pin with a hole for pulling, enabling the rocker arm to rotate around the pin with a hole for pulling; the lower end of the vertical U-shaped strut is also sleeved on the pin with a hole for pulling and is located at both ends of the pin with a hole for pulling; The double-ended lever is hinged to one end of the main buffer; the other end of the main buffer is hinged to the upper end of the rocker arm lug; the lower end of the rocker arm lug is connected to the rocker arm; the side retraction and extension actuator is located on one side of the main buffer; the upper end of the vertical U-shaped strut is hinged to the rear landing gear fixing part located in the landing gear compartment of the aircraft; One end of the side retraction and extension actuator is hinged to the fuselage fixing part, and the other end is connected to the diagonal girder through a pin with a hole for pulling; One end of the double-ended lever actuator (7) is connected to the lug at the center position of the web on the bottom side of the diagonal girder (6), and the other end is hinged to the double-ended lever (8).

2. The three-stage retractable rocker-type landing gear according to claim 1, characterized in that, The vertical U-shaped strut includes an inner U-shaped frame, an outer U-shaped frame and a plurality of support rods; there is a through hole for connecting to the rear landing gear fixing part at the top of the arc-shaped rod of the outer U-shaped frame; a plurality of support rods are provided between the outer arc surface of the inner U-shaped frame and the inner arc surface of the outer U-shaped frame; the two side plates at the open end of the inner U-shaped frame are respectively connected to the two side plates at the open end of the outer U-shaped frame on the corresponding side; there are through holes for connecting to the diagonal girder on the two side plates at the U-shaped open end of the vertical U-shaped strut; the distance between the two side plates of the vertical U-shaped strut meets the connection requirements of the large end of the diagonal girder.

3. The rocker-type landing gear capable of three-stage retraction as claimed in claim 1, wherein, There are installation holes for the diagonal girder pin and installation holes for the double-ended lever fulcrum axis at the small end of the diagonal girder, and there are connection holes for the vertical U-shaped strut at the large end of the diagonal girder; the inner width of the diagonal girder meets the installation of the main buffer.

4. The three-stage retractable rocker-type landing gear according to claim 1, wherein There is a through hole for hinging at the intersection of the angle bisectors of the double-ended lever; there are U-shaped grooves at the two bottom corners of the double-ended lever, and each U-shaped groove penetrates the surfaces of the two hypotenuses and the bottom of the double-ended lever; there are coaxial through holes on both side walls of the U-shaped groove.

5. The rocker-type landing gear capable of three-stage retraction and extension according to claim 1, characterized in that, The retraction and extension process of the three-stage rocker arm type landing gear is as follows: The first-stage retraction process of the landing gear: The aircraft oil pump operates, and the oil in the squatting cavity of the main buffer is released, causing the inner cylinder to contract and pulling the rocker arm to rotate around the pin with a pulling hole by a certain angle; during this process, the retraction is a large-scale retraction; when the landing gear is retracted or extended, the main buffer is used as an actuator, that is, the squatting cavity is enabled; the main buffer contracts and locks in the upper position / retracted position, pulling the rocker arm and the wheel upward for retraction; The second-stage retraction process of the landing gear: After the main buffer contracts and locks in the upper position, the double-ended lever actuator generates a pulling force on one end of the long arm of the double-ended lever. At this time, an upward pulling force is generated at one end of the short arm where the double-ended lever is hinged to the outer cylinder of the main buffer. At this time, the main buffer can be regarded as a transmission part, and the other end of the main buffer pulls the rocker arm to further rotate around the pin with a pulling hole by a certain angle; the secondary retraction action is completed; The third-stage retraction process of the landing gear: The side retraction / extension actuator is activated to generate a pulling force, which acts on the pin with a pulling hole, driving the entire landing gear to rotate around the heading by a certain angle and be stored in the landing gear bay, completing the tertiary retraction action; the working process of extension is the opposite.

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