Two-stage series double-cavity buffer and helicopter undercarriage

Abstract

The two-stage series double-cavity buffer comprises a low-pressure-stage buffer body and a high-pressure-stage buffer body, an inner cavity of the low-pressure-stage buffer body is divided into a first cavity and a second cavity by a floating piston, a deflation valve is installed at the end, away from the floating piston, of the first cavity, and a low-pressure-stage damping valve is installed in the second cavity; an inner cavity of the high-pressure-stage buffer is divided into a third cavity and a fourth cavity by the high-pressure-stage damping valve, a rupture disk is installed in a damping hole of the high-pressure-stage damping valve, and the third cavity and the fourth cavity are isolated through the rupture disk to form independent cavities. The low-pressure-stage outer cylinder is connected with the high-pressure-stage outer cylinder in series, in the normal working condition, the high-pressure-stage piston rod extends out of the high-pressure-stage outer cylinder, the high-pressure-stage outer cylinder is fixedly connected with the high-pressure-stage piston rod through the emergency shearing device, in the abnormal working condition, the emergency shearing device is sheared off, the rupture disk is pressed to be exploded, and the third cavity and the fourth cavity are communicated through the high-pressure-stage damping valve.

Description

Technical Field

[0001] This invention relates to helicopter landing gear, specifically to a two-stage series dual-cavity buffer and helicopter landing gear. Background Technology

[0002] The military applications of attack helicopters (including flight requirements under both operational and natural environmental conditions) significantly increase the likelihood of crashes. Furthermore, due to their unique rotor structure, attack helicopters lack the ejection escape equipment common to fixed-wing aircraft. Therefore, employing crashworthiness design technologies is an effective way to protect pilots and crew members in attack helicopters.

[0003] The crashworthiness of helicopter landing gear plays a crucial role in the overall crashworthiness system and is the first link in the crashworthiness energy absorption chain. The crashworthiness of the landing gear directly determines the helicopter's survivability. At the same time, the design of helicopter landing gear must minimize landing overload during daily use. This results in a very wide operating load range for helicopter landing gear: it must ensure low overload at low speeds to meet long-life requirements, while simultaneously using efficient energy-absorbing buffers to prevent excessive overload at high descent speeds. Early traditional helicopter landing gear, due to the required descent speed of approximately 6 m / s, often employed a series two-stage hydrant-pneumatic buffer. During normal use, the low-pressure chamber absorbed energy, while the high-pressure chamber absorbed energy at higher landing speeds. The current US military standard MIL-STD-1290A and the Chinese military standard GJB2681A-2015 require military helicopters to withstand crashes at speeds up to 12.8 m / s. The requirements are that the landing gear system should absorb at least 60% of the crash energy at such high descent speeds, without hindering the fuselage and pilot's seat from absorbing further energy.

[0004] As the helicopter's crashworthiness descent speed further increases to as high as 12.8 m / s, the landing gear buffer adopts a hydropneumatic separation structure. At high descent speeds, during the initial stage of the buffer's violent compression, the damping force in the oil chamber increases exponentially, forming a considerable peak hydraulic load within the buffer cavity. This hydraulic damping load quickly leads to landing gear structural failure or the failure of airframe components. When the buffer is compressed to the end of its stroke, the compressed gas load increases sharply, generating a peak gas load. This gas load also leads to rapid damage to the airframe structure. At the same time, due to the extremely short energy absorption time of the hydropneumatic buffer at high descent speeds, approximately 0.1 to 0.15 seconds, the energy absorption efficiency of the buffer during crash landing is low and cannot meet the overall technical requirement of 60% of the total impact energy of the entire aircraft. Summary of the Invention

[0005] The technical problem to be solved by this invention is that, in the case of traditional helicopter landing gear using a series dual-cavity hydrant-pneumatic buffer, the load on the hydrant-pneumatic cavity is unstable and the energy absorption efficiency is low during a crash. This invention provides a two-stage series dual-cavity buffer and helicopter landing gear that meets the energy absorption requirements for takeoff and landing under normal operating conditions of the landing gear and can improve the energy absorption efficiency of the landing gear during a crash.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A two-stage series dual-cavity buffer, comprising a low-voltage stage buffer and a high-voltage stage buffer, is characterized by the following structural features: The low-pressure stage buffer includes a low-pressure stage piston rod, a low-pressure stage outer cylinder, and a floating piston. The low-pressure stage piston rod is slidably installed inside the low-pressure stage outer cylinder. The floating piston is installed in the inner cavity of the low-pressure stage piston rod, and the floating piston divides the inner cavity of the low-pressure stage buffer into a first cavity for filling with gas and a second cavity for filling with hydraulic oil. A vent valve is installed at the end of the first cavity away from the floating piston. A low-pressure stage damping valve is installed in the second cavity. The low-pressure stage damping valve divides the second cavity into a first part and a second part. The first part and the second part communicate through a damping orifice on the low-pressure stage damping valve. The high-pressure stage buffer includes a high-pressure stage piston rod and a high-pressure stage outer cylinder. The high-pressure stage piston rod is slidably installed inside the high-pressure stage outer cylinder. A high-pressure stage damping valve is installed in the inner cavity of the high-pressure stage piston rod. The high-pressure stage damping valve divides the inner cavity of the high-pressure stage buffer into a third cavity and a fourth cavity for filling with hydraulic oil. A rupture disc is installed in the damping orifice of the high-pressure stage damping valve. The third cavity and the fourth cavity are isolated by the rupture disc to form independent and closed cavities. The low-pressure stage outer cylinder is connected in series with the high-pressure stage outer cylinder. Under normal operating conditions, the high-pressure stage piston rod extends out of the high-pressure stage outer cylinder. The high-pressure stage outer cylinder and the high-pressure stage piston rod are fixedly connected by an emergency shear. Under abnormal operating conditions, the emergency shear cuts off the piston, and the rupture disc bursts under pressure. The third cavity and the fourth cavity are connected by the high-pressure stage damping valve.

[0007] A further improvement to the above scheme is that the low-pressure damping valve and the high-pressure damping valve are respectively mounted on the bushing.

[0008] A further improvement to the above scheme is that the venting valve is a cam valve.

[0009] A further improvement to the above scheme is that the first cavity is filled with nitrogen, and the second, third, and fourth cavities are filled with aviation hydraulic oil, respectively.

[0010] A further improvement to the above scheme is that the low-pressure stage outer cylinder and the high-pressure stage outer cylinder are an integral structure.

[0011] A further improvement to the above scheme is that the ends of the low-pressure stage piston rod and the high-pressure stage piston rod are respectively equipped with spherical bearings.

[0012] A further improvement to the above scheme is that a first inflation valve for inflating the first cavity is arranged on the low-pressure stage piston rod, a second inflation valve for venting is arranged in the middle of the high-pressure stage outer cylinder, and a plug and sealing ring for injecting oil into the high-pressure stage buffer are installed on the high-pressure piston rod.

[0013] Based on the same inventive concept, the present invention also provides a helicopter landing gear, including a rocker arm assembly, a buffer assembly and a wheel. One end of the rocker arm assembly is connected to the wheel and the other end is connected to the fuselage. The buffer assembly is a two-stage series dual-cavity buffer, and one end of the buffer assembly is connected to the fuselage and the other end is connected to the middle part of the rocker arm assembly.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1) The high crashworthiness helicopter landing gear provided by the present invention can maximize the energy absorption efficiency of the entire landing gear system. At the same time, it can meet the energy absorption index requirements for takeoff and landing under normal operating conditions of the landing gear, and solve the shortcomings of traditional helicopter landing gear series dual-chamber oil-gas buffers such as unstable oil-gas chamber load and low energy absorption efficiency during the crash.

[0015] 2) When the helicopter landing gear is parked on the ground, the first cavity can be emptied or deflated by the first inflation valve connected to the first cavity to adjust the buffer length and thus adjust the center of gravity of the helicopter. This makes it easier for ground crew to load weapons or unload cargo, and also facilitates the requirements of the helicopter crouching and air transport installation in large transport aircraft. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the two-stage series dual-cavity buffer of the present invention; Figure 2 This is a schematic diagram of the helicopter landing gear of the present invention; Figure 3 This is a schematic diagram of the attitude of the helicopter landing gear under various working conditions according to the present invention. Figure 4This is a schematic diagram showing the structural composition and functional principle of the landing gear and buffer under takeoff conditions, where a is the landing gear state diagram and b is the buffer assembly state diagram. Figure 5 This is a schematic diagram showing the structure and function of the landing gear and buffer under shutdown conditions, where a is the landing gear state diagram and b is the buffer assembly state diagram. Figure 6 This diagram illustrates the structural composition and functional principle of the landing gear and buffers under maintenance and air transport conditions. Diagram a shows the landing gear status and diagram b shows the buffer assembly status. Figure 7 This is a schematic diagram of the landing gear compression and energy absorption process under crash conditions. Figure 8 This is a schematic diagram showing the structure and function of the landing gear and buffer under crash conditions, where a is the landing gear state diagram and b is the buffer assembly state diagram.

[0018] In the diagram: 1-Earring connector; 2-Deflator valve; 3-Low-pressure stage piston rod; 4-Floating piston; 5-Sleeve; 50-Low-pressure stage damping valve; 6-Outer cylinder; 7-Sleeve; 70-High-pressure stage damping valve; 8-Emergency shears; 9-High-pressure stage piston rod; 10-First inflation valve; 11-Second inflation valve; 100-Buffer assembly; 200-Rocker arm assembly; 300-Wheel; 1001-Low-pressure stage buffer; 1002-High-pressure stage buffer; Ⅰ-First chamber; Ⅱ-Second chamber; Ⅲ-Third chamber; Ⅳ-Fourth chamber. Detailed Implementation

[0019] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0020] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] Please see Figure 1 An embodiment of the two-stage series dual-cavity buffer of the present invention includes a low-voltage stage buffer 1001 and a high-voltage stage buffer 1002 connected in series.

[0023] The low-pressure stage buffer 1001 includes a low-pressure stage piston rod 3, a low-pressure stage outer cylinder 6, a floating piston 4, and a low-pressure stage damping valve 50. The low-pressure stage piston rod 3 is slidably installed inside the low-pressure stage outer cylinder 6. The floating piston 4 is installed in the inner cavity of the low-pressure stage piston rod 3, and the floating piston 4 divides the inner cavity of the low-pressure stage buffer into a first cavity I for filling with high-purity nitrogen and a second cavity II for filling with aviation hydraulic oil. A vent valve 2 is installed at the end of the first cavity I away from the floating piston for venting and unloading under extreme operating conditions. The low-pressure stage damping valve 50 is installed in the second cavity II, and the low-pressure stage damping valve 50 divides the second cavity II into a first part and a second part. The first part and the second part communicate through a damping orifice on the low-pressure stage damping valve 50, and hydraulic oil can flow from the second part into the first part through the damping orifice on the low-pressure stage damping valve 50. The low-pressure stage damping valve 50 consists of a valve seat, a spring, a gasket, etc.

[0024] The high-pressure stage buffer 1002 includes a high-pressure stage piston rod 9 and a high-pressure stage outer cylinder 6. The high-pressure stage piston rod 9 is slidably installed inside the high-pressure stage outer cylinder 6. A high-pressure stage damping valve 70 is installed in the inner cavity of the high-pressure stage piston rod 9. The high-pressure stage damping valve 70 divides the inner cavity of the high-pressure stage buffer into a third cavity III and a fourth cavity IV for filling aviation hydraulic oil. A rupture disc (not shown in the figure) is installed in the damping orifice of the high-pressure stage damping valve 70. The third cavity III and the fourth cavity IV are isolated by the rupture disc to form independent and closed cavities, so that the hydraulic oil in the third cavity III and the fourth cavity IV is isolated by the rupture disc and sealing ring built into the high-pressure stage damping valve 70.

[0025] Under normal operating conditions, the high-pressure stage outer cylinder 6 and the high-pressure stage piston rod 9 are fixedly connected by the emergency shear 8. Under abnormal operating conditions, the emergency shear 8 cuts off, the rupture disc is compressed and explodes, and the third chamber III and the fourth chamber IV are connected by the high-pressure stage damping valve 70.

[0026] The low-pressure stage damping valve 50 is installed on the low-pressure stage bushing 4 made of aluminum bronze and is connected to the low-pressure stage outer cylinder 6 via the low-pressure stage bushing 4. The high-pressure stage damping valve 70 is installed on the high-pressure stage bushing 7 made of aluminum bronze and is connected to the high-pressure stage outer cylinder 6 via the high-pressure stage bushing 7.

[0027] The venting valve 2 is preferably a cam valve.

[0028] To simplify the structure, the low-pressure stage outer cylinder 6 and the high-pressure stage outer cylinder 6 are integrated into one unit.

[0029] For ease of connection, the ends of the low-pressure stage piston rod 3 and the high-pressure stage piston rod 9 are respectively equipped with spherical bearings.

[0030] Furthermore, a first inflation valve 10 is arranged at the end of the low-pressure stage piston rod 3 for inflating the first cavity I; a second inflation valve 11 is arranged in the middle of the high-pressure stage outer cylinder 6 for venting air from the high-pressure buffer 1002; and a plug and sealing ring are installed at the end of the high-pressure piston rod 9 for injecting oil into the high-pressure stage buffer 1002.

[0031] Please see Figure 2 This invention discloses a helicopter landing gear embodiment employing a full rocker arm structure, primarily composed of a rocker arm assembly 200, a shock absorber assembly 100, and wheels 300. One end of the rocker arm assembly 200 is connected to the wheels via an axle, and the other end is connected to the fuselage (helicopter fuselage, not shown in the figure) via a self-lubricating bushing. The shock absorber assembly 100 is a key component for energy absorption in the landing gear; the shock absorber assembly 100 in this invention is a two-stage, series-connected, dual-chamber shock absorber assembly. The low-pressure stage piston rod 3 of the shock absorber assembly 100 is connected to a corresponding connector on the fuselage via an eyelet connector 1, and the high-pressure stage piston rod 9 of the shock absorber assembly 100 is bolted to the two lugs located in the middle of the rocker arm assembly 200. The operating principle of this invention's helicopter landing gear under takeoff (no external load), parking, taxiing, normal landing, crash, and air transport conditions is as follows: like Figure 3 , Figure 4 As shown, when the helicopter takes off, the main landing gear has no external load. Under the action of high-pressure gas in the nitrogen chamber inside the first chamber I of the low-pressure stage buffer, the low-pressure stage piston rod 3 moves outward and extends. After the low-pressure stage piston rod 3 extends, it drives the rocker arm assembly 200 to rotate clockwise and keep the landing gear in the fully extended position.

[0032] like Figure 3 , Figure 5 As shown, when the helicopter is parked on the ground, the low-pressure stage buffer 1001 bears a pressure load under the weight of the aircraft. This pressure load pushes the low-pressure stage piston rod 3 into the low-pressure stage outer cylinder 6, compressing the oil in the second part of the second chamber II. The oil enters the first part after passing through the damping hole on the low-pressure stage damping valve 50 and pushes the floating piston 4 to the left, making the volume of the first chamber I (air chamber) smaller and the pressure increase. The internal high-pressure gas rises until it is balanced with the external load, keeping the aircraft in a parked position and realizing its load-bearing function.

[0033] like Figure 3 , Figure 6As shown, when the helicopter needs maintenance and air transport, the gas in the first chamber I (gas chamber) of the low-pressure stage buffer is released through the first inflation valve 10 of the low-pressure stage buffer 1001. Under the weight of the fuselage, the low-pressure stage piston rod 3 continues to compress from the stop position. The oil continues to enter the first part after passing through the damping hole of the low-pressure stage damping valve 50 and pushes the floating piston 4 to move to the left. After the low-pressure stage piston rod 3 is compressed, it drives the rocker arm assembly 200 to rotate counterclockwise. After the low-pressure stage piston rod 3 continues to compress for a certain period of time, the end face of the low-pressure stage piston rod 3 contacts the bottom of the low-pressure stage outer cylinder 6 and stops, keeping the landing gear in a squatting position and reducing the overall height of the fuselage, thereby meeting the requirements for air transport and maintenance of the helicopter on large transport aircraft.

[0034] like Figure 3 , Figure 7 and Figure 8 As shown, when the helicopter crashes, as it falls freely at a descent speed of 12.8 m / s, the tires and low-pressure stage piston rod 3 are initially compressed violently. After the low-pressure stage piston rod 3 has compressed to a certain stroke, the emergency shear device 8 on the high-pressure stage buffer 1002 cuts off, unlocking the stroke of the high-pressure stage piston rod 9. After the high-pressure stage piston rod 9 has moved a certain stroke, the rupture disc inside the high-pressure stage damping valve 70 explodes, further compressing the low-pressure stage piston rod 3 and the high-pressure stage piston rod 9 until the low-pressure stage buffer 1001 and the high-pressure stage buffer... When the pressure inside the 1002 cavity reaches a uniform level, the oil in the low-pressure stage buffer 1001 and the high-pressure stage buffer 1002 further absorbs energy through the damping orifice. After the low-pressure stage piston rod 3 is compressed to its end stroke under the damping force of the oil in the cavity, the gas load inside the first chamber I increases dramatically. At this time, the floating piston 4 also moves to the end of its stroke. The push rod on the floating piston 4 pushes the vent valve 2. After the vent valve 2 rotates, it discharges the gas in the first chamber I to the atmosphere, so that the energy stored in the gas in the first chamber I is discharged and dissipated. With the further movement of the floating piston 4, both the low-pressure stage buffer 1001 and the high-pressure stage buffer 1002 are finally in a fully compressed state, thereby realizing the anti-fall function of the high-drop-resilience buffer.

[0035] When in use, the helicopter landing gear of this invention is symmetrically arranged on both sides of the helicopter fuselage structure. The lateral load of the helicopter is transmitted to the helicopter fuselage by the rocker arm assembly 200 through the fuselage connection joint. The buffer assembly 100 only bears the axial load and will not jam. As can be seen from the above principle, when the helicopter lands or crashes, the landing load can maintain a relatively gradual change, avoiding load spikes. At the same time, before the crash, because the high-pressure stage piston rod 9 is fully extended from the high-pressure stage outer cylinder 6 and connected and fixed by the emergency shear 8, the fuselage has a high altitude off the ground. During the crash, the high altitude of the fuselage can be fully utilized to absorb the crash energy.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can make many possible variations and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention should fall within the scope of protection of the technical solution of the present invention.

Claims

1. A two-stage series double-cavity buffer comprising a low-pressure stage buffer and a high-pressure stage buffer, characterized in that: the low-pressure stage buffer comprises a low-pressure stage piston rod, a low-pressure stage outer cylinder, and a floating piston, the low-pressure stage piston rod is slidingly installed in the low-pressure stage outer cylinder, the floating piston is installed in the inner cavity of the low-pressure stage piston rod, and the floating piston divides the inner cavity of the low-pressure stage buffer into a first cavity for filling gas and a second cavity for filling hydraulic oil, a gas release valve is installed at the end of the first cavity away from the floating piston, a low-pressure stage damping valve is installed in the second cavity, the low-pressure stage damping valve divides the second cavity into a first part and a second part, and the first part and the second part communicate through a damping hole on the low-pressure stage damping valve; the high-pressure stage buffer comprises a high-pressure stage piston rod and a high-pressure stage outer cylinder, the high-pressure stage piston rod is slidingly installed in the high-pressure stage outer cylinder, a high-pressure stage damping valve is installed in the inner cavity of the high-pressure stage piston rod, the high-pressure stage damping valve divides the inner cavity of the high-pressure stage buffer into a third cavity for filling hydraulic oil and a fourth cavity, a rupture disc is installed in the damping hole of the high-pressure stage damping valve, and the third cavity and the fourth cavity are isolated from each other by the rupture disc to form independent and closed cavities; the low-pressure stage outer cylinder and the high-pressure stage outer cylinder are connected in series, under normal working conditions, the high-pressure stage piston rod extends out of the high-pressure stage outer cylinder, the high-pressure stage outer cylinder and the high-pressure stage piston rod are fixedly connected through an emergency cutter, under abnormal working conditions, the emergency cutter is cut, the rupture disc is burst under pressure, and the third cavity and the fourth cavity communicate through the high-pressure stage damping valve. The low-pressure stage damping valve and the high-pressure stage damping valve are respectively installed on a shaft sleeve. The gas release valve is a cam valve. The first cavity is filled with nitrogen, and the second cavity, the third cavity, and the fourth cavity are respectively filled with aviation hydraulic oil.

2. The two-stage series dual cavity absorber of claim 1, wherein, The low-pressure stage outer cylinder and the high-pressure stage outer cylinder are of an integrated structure.

3. The two-stage series dual chamber damper according to claim 1, wherein, The end of the low-pressure stage piston rod and the end of the high-pressure stage piston rod are respectively installed with a joint bearing.

4. The two-stage series dual chamber damper of claim 1, wherein, A first gas charging valve for charging the first cavity is arranged on the low-pressure stage piston rod, a second gas charging valve for discharging is arranged in the middle part of the high-pressure stage outer cylinder, and a plug and a sealing ring for injecting oil into the high-pressure stage buffer are installed on the high-pressure piston rod.

5. The two-stage series dual chamber damper of claim 1, wherein, One end of the rocker arm assembly is connected with the machine wheel, the other end is connected with the machine body, the buffer assembly is the two-stage series double-cavity buffer according to any one of claims 1-7, and one end of the buffer assembly is connected with the machine body, and the other end is connected with the middle part of the rocker arm assembly.

6. The two-stage series dual chamber damper of claim 1, wherein, ​ 7. The two-stage series dual chamber damper of claim 1, wherein, ​ 8. A helicopter landing gear comprising a rocker assembly, a shock absorber assembly and a wheel, characterised in that, ​

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