Sleeve, sleeve manufacturing method, shaft assembly, landing gear assembly and aircraft

Abstract

Wheel aircraft landing gears usually comprise a sleeve (10) arranged to protect a shaft (9). Vibration of the brake system and bending of the shaft can cause the shaft (9) and the sleeve (10) to rub and rotate relative to each other, thereby increasing the temperature in this area and causing damage to the sleeve and / or the shaft. The invention provides a sleeve (10) having a low friction wear surface (19) on a portion of, for example, the inner surface. The low friction wear surface (19) comprises a ring (20) of a composite material, such as fibres in a polymer matrix. The invention also relates to a shaft assembly comprising such a sleeve, a landing gear assembly and an aircraft. Furthermore, the invention also relates to a method of manufacturing such a sleeve.

Description

Technical Field

[0001] This invention relates to sleeves for shafts, such as shafts in aircraft landing gear assemblies. The invention also relates to shaft assemblies, aircraft landing gear assemblies, and aircraft themselves, all of which include such sleeves. The invention further relates to methods of manufacturing such sleeves. Background Technology

[0002] The landing gear of an aircraft supports the aircraft upon landing, allowing for takeoff, landing, and taxiing. Wheeled landing gear is the most common type, and therefore, landing gear assemblies typically include an axle rotatably mounted with a set of wheels. The axle also supports a portion of the wheels for the braking assembly. After a period of operation, the tires and brakes of the wheel assembly wear down and therefore need to be removed for maintenance or replacement. During this removal and replacement of these components, the axle may be damaged. Axles are heavy-duty load-bearing components, typically made of forged steel. Replacing a damaged axle is very difficult, time-consuming, and expensive. Therefore, protective sleeves are provided for the axles. Sleeves are easier to replace than the entire axle when damaged and are therefore considered consumable components of the landing gear assembly.

[0003] As mentioned above, landing gear assemblies typically also include braking assemblies, which consist of a combination of rotating and stationary components. During braking, the aircraft's anti-skid system adjusts the torque applied to the braking assembly to prevent tire slippage and damage, and to maximize braking efficiency under all ground / runway conditions. Torque variations and the associated subsequent changes in wheel speed can cause corresponding rotational oscillations in the shaft sleeve on the shaft. This oscillation and bending of the shaft under load can cause the shaft and sleeve to rub together, increasing the temperature in that area and causing thermal damage and / or wear to the shaft, sleeve, or both. This fretting results in the need for more frequent sleeve replacements, which is both expensive and inconvenient.

[0004] It has been proposed to reduce damage caused by fretting by providing lubricant at the interface between the sleeve and the shaft. However, vibrations and heat generated by the braking system cause this lubricant to dissipate, necessitating periodic reapplication. This adds an extra maintenance burden.

[0005] A method to prevent fretting was also proposed: increasing the spacing between the sleeve and the shaft in the vicinity of the braking system. However, due to the arrangement of the braking system and other landing gear components, and its proximity to these other components, it is difficult to provide such additional spacing. Summary of the Invention

[0006] This invention provides a sleeve for an aircraft landing gear shaft with a low-friction surface, the low-friction surface comprising a composite material ring on a portion of the sleeve's surface. The low-friction surface allows the sleeve to move relative to other components, such as the shaft, without causing wear or thermal damage to the sleeve or other components.

[0007] Preferably, the composite material includes fibers in a polymer matrix, such as polytetrafluoroethylene.

[0008] Advantageously, the fibers include the following options: glass; carbon; Kevlar; basalt; PTFE; cotton; wood and / or paper.

[0009] Preferably, the low-friction wear surface is located on the inner surface of the sleeve and is arranged to engage with the shaft during use or with another part of the landing gear assembly, such as a part of the braking assembly.

[0010] The low-friction wear surface can be arranged above the inner surface so that it is inserted between the sleeve and the shaft.

[0011] Advantageously, multiple low-friction wear surfaces in the form of composite rings can be provided on different corresponding portions of the sleeve surface. These can be inner surfaces, outer surfaces, or a combination of both.

[0012] The present invention also provides a method for manufacturing an aircraft landing gear shaft sleeve, the method comprising the steps of: forming a low-friction wear surface; and bonding the low-friction wear surface to the surface of the sleeve.

[0013] Preferably, the step of forming a low-friction surface includes manufacturing a ring of a composite material comprising fibers in a polymer matrix. This step may include manufacturing a fiber preform and then introducing it into the polymer matrix.

[0014] The step of incorporating the low-friction wear surface preferably includes in-situ curing the low-friction wear surface on the surface of the sleeve. The low-friction wear surface can then be machined to a predetermined size.

[0015] The present invention also provides an aircraft landing gear shaft assembly, which includes a shaft and a sleeve of the present invention disposed circumferentially around the shaft.

[0016] Advantageously, the coefficient of friction between the low-friction wear surface and the shaft is less than the coefficient of friction between the inner surface of the sleeve and the shaft. The coefficient of friction between the low-friction wear surface and the shaft is less than 0.4 μ.

[0017] The present invention also provides an aircraft landing gear assembly that includes the shaft assembly of the present invention.

[0018] An aircraft landing gear assembly may include a column supported by a pair of such shaft assemblies. Several pairs of shaft assemblies may be provided.

[0019] Preferably, a braking system is also provided, wherein the sleeve is arranged such that a low-friction wear surface is located at the end portion of the sleeve adjacent to a portion of the braking system.

[0020] The present invention also includes an aircraft comprising at least one aircraft landing gear assembly of the present invention. Attached Figure Description

[0021] The invention will now be described by way of example with reference to the accompanying drawings, in which:

[0022] Figure 1 This is a front view of the aircraft;

[0023] Figure 2 yes Figure 1 A perspective view of a portion of the landing gear of an aircraft, the landing gear including a bushing constructed according to the present invention;

[0024] Figure 3a yes Figure 2 A cross-sectional view of the axis along its longitudinal axis;

[0025] Figure 3b yes Figure 3a An enlarged view of a portion circled in dashed lines;

[0026] Figure 4 yes Figure 2 And the cross-sectional view of the shaft and sleeve along the dashed line A-A' in Figure 3; and

[0027] Figure 5 It is manufacturing Figures 2 to 4 The flowchart shows the method for using a shaft sleeve.

[0028] Detailed description of the implementation methods of this technology

[0029] In the examples described in this article, the reference to “aircraft” includes all types of aircraft, such as fixed-wing military or commercial aircraft; unmanned aerial vehicles (UAVs); and rotorcraft, such as helicopters.

[0030] The components shown in the diagram are not necessarily shown to scale.

[0031] Reference Figure 1The aircraft, generally indicated by reference numeral 1 in the attached figure, comprises a pair of wings 2a and 2b and a fuselage 3. Wings 2a and 2b each carry engines 4a and 4b, respectively. In this example, the aircraft 1 is supported on the ground by a landing gear assembly comprising a main landing gear (MLG) 5 and a nose landing gear (NLG) 6. The landing gear assembly includes multiple pairs of wheel assemblies 7. Figure 1 The aircraft is shown in contact with the ground (e.g., a runway). It has a total of six wheel assemblies; four wheel assemblies are part of the MLG 5, and two wheel assemblies are part of the nose landing gear NLG 6. Of course, other landing gear arrangements with any number of single-wheel units or bogies consisting of multiple wheels can also be provided.

[0032] exist Figure 2 The simplified diagram shows Figure 1 This is a portion of a landing gear assembly. In this figure, only one of the main support column 8 and shaft 9 of the landing gear assembly is shown. Another shaft (not shown) is also provided, extending from the other side of the main support column 8. Together, the shafts support the wheel assembly 7 of the landing gear assembly. Each landing gear shaft 9 is provided with a protective sleeve 10. The sleeve 10 is formed from a steel tube, typically a single piece, and its shape is arranged to correspond to the dimensions of the shaft 9. The sleeve 10 is arranged to protect the shaft 9 and the wheel assembly 7 during use.

[0033] Now refer to Figure 2 , Figure 3a and Figure 3b The sleeve 10 includes multiple regions arranged to engage with different components of the landing gear. For example, the inner end of the sleeve 10 (i.e., the end portion of the sleeve in use closer to the post 8) is arranged to abut against the flange 11. The stationary portion of the aircraft braking system (not shown in these figures) is typically bolted to this flange 11. The outer end of the sleeve 10 (i.e., the end portion of the sleeve in use farther from the post 8) is held by a nut 12 connected to the tip 13 of the shaft. The nut 12 is arranged to hold the entire wheel assembly 7 in place on the shaft 9.

[0034] The shaft assembly also includes a plurality of journals 14, 15, and 16 in the area where the shaft 9 and the sleeve 10 contact. The outer journal 14 includes the outer portion of the receiving wheel assembly of the sleeve 10, such as a section of the outer wheel bearing 17. The intermediate journal 15 includes the inner portion of the receiving wheel assembly of the sleeve 10, such as a section of the inner wheel bearing 18.

[0035] The inner journal 16 is the innermost region of the sleeve 10 that contacts the shaft 9. The inner journal 16 is the part of the sleeve 10 most susceptible to fretting caused by vibrations from the braking system and bending of the shaft 9 against the sleeve. According to the invention, this inner region of the sleeve 10 includes a low-friction wear surface 19 attached to the inner surface of the sleeve 10. The low-friction wear surface 19 is inserted between the shaft 9 and the body of the sleeve 10, and... Figure 3b The magnified image shows that... and in Figure 4 It is also visible in the cross-sectional view.

[0036] The low-friction wear surface 19 includes a ring 20 formed of a composite material containing fibers in a polymer matrix. The ring 20 has a thickness of less than one millimeter (in the radial direction): a typical value for this application is approximately 0.3 mm. The ring 20 is formed by a circular wall extending several centimeters (in the axial direction), typically about 3.5 cm. The low-friction wear surface 19, including the interface between the ring 20 and the shaft 9, benefits from the polymer matrix having a low coefficient of friction typically less than 0.4 μ. The coefficient of friction between the sleeve and the shaft can be determined by the choice of fibers and the fraction of fibers in the matrix; the coefficient of friction value can be as low as 0.03 μ.

[0037] The fibers in ring 20 provide strength and durability to increase the lifespan of the low-friction wear surface 19. In this embodiment, the ring is formed of a composite material comprising fibers in a polytetrafluoroethylene (PTFE) matrix. The fibers can be made of any suitable material, such as glass, carbon, Kevlar, basalt, or even PTFE yarn. Any combination of these fibers can be used.

[0038] During use, the low-friction wear surface 19 allows the shaft and sleeve to bend, slide, and rotate relative to each other. The sleeve also better tolerates vibrations caused by the braking system. The composite ring 20 is also able to withstand the extreme temperatures experienced by the landing gear assembly during use. Furthermore, the ring 20 is advantageously lightweight, ensuring that it will not affect the balance of the landing gear assembly.

[0039] Over time, the movement of ring 20 against the shaft will cause the ring to gradually wear. This low-impact degradation is advantageous because it does not damage other components of the landing gear assembly. Ring 20 is a sacrificial element of the landing gear assembly. When the ring wears out, sleeve 10 can be replaced during maintenance with a sleeve having a new composite ring 20 on the inner surface of the sleeve.

[0040] Figure 5 This is a flowchart illustrating an example method for manufacturing a bushing constructed according to the present invention.

[0041] Step 21 involves manufacturing a fiber preform. This can be achieved by braiding, weaving, or knitting the fibers to form a fabric layer of the desired shape and size. Alternatively, a nonwoven mat of short fibers can be cut into a specific shape. The fiber preform is then laid in a mold having the same dimensions as sleeve 10. Alternatively, the fiber preform can be wound onto a tubular mandrel having an outer diameter slightly smaller than the inner diameter of sleeve 10, for example, 1 mm smaller.

[0042] Once the preform has stabilized, the next step 22 involves infusing the preform with a liquid polymer. This can be accomplished by any suitable method known to those skilled in the art, such as injection molding, resin transfer molding, or cold pressing and sintering.

[0043] The third step 23 involves curing the composite ring 20. This is done in situ within the sleeve 10. The ring 20 is positioned in the desired location within the sleeve 10. (See Figure 3 and...) Figure 4 In the embodiment shown, the ring 20 is held at the end portion corresponding to the inner part of the sleeve during use. The ring 20 is then heated to a predetermined curing temperature. This temperature is maintained for a predetermined time until curing is complete. Pressure may also be applied to bond the ring 20 to the inside of the sleeve 10. The sleeve 10 and the ring 20 are then cooled in a controlled manner.

[0044] The final step, 24, is machining via milling, routing, sanding, or any combination of these processes. The ring 20 can be machined to the desired dimensions such that it protrudes above the inner surface of the sleeve 10 by a predetermined, desired amount; as mentioned above, this is typically a fraction of a millimeter. Compressed air can be applied during this process to remove chips.

[0045] Variations may be made without departing from the scope of the invention. For example, the sleeve need not be a cylindrical tube of constant diameter. The sleeve may include a conical cross-section, or may have different shapes in different corresponding regions of the sleeve.

[0046] Other polymers, such as epoxy resins or polyetheretherketone (PEEK), can be used as the matrix. Combinations of polymers can be employed. Mineral fillers, such as silicates, can be used in the matrix material. This invention is more sustainable by using natural fibers such as cotton, wood, or paper to manufacture composite fiber preforms.

[0047] As an alternative to fixing the ring 20 to the inner surface of the sleeve, a seat can be cut into the inner surface of the sleeve 10, and the ring can be engaged into the seat. This can hold the ring more securely. The ring 20 can be designed to engage with the sleeve or the seat in the sleeve in a snap-fit ​​manner. Alternatively, the ring can engage with the sleeve in an interference fit, engage with the sleeve itself, or engage in a corresponding groove in the sleeve.

[0048] The position of ring 20 is not limited to the location shown in the figure. Ring 20 may alternatively or additionally be provided at the interface between outer journal 14 and shaft 9 and / or at the interface between intermediate journal 15 and shaft. Ring 20 may also be provided at the inner end of sleeve 10, for example at flange 11, to protect sleeve from damage at engagement with components of the braking assembly. Each ring need not have the same composition: different fibers, polymers, or fiber fractions may be used depending on the desired coefficient of friction and wear performance at the interface between sleeve and component.

[0049] As an alternative, ring 20 may be disposed on a portion of the outer surface of sleeve 10 to prevent damage from contact with other components of the landing gear assembly, such as brakes. Other variations will be apparent to a technician.

Claims

1. A shaft assembly for an aircraft landing gear, comprising: axis; A sleeve, the sleeve being circumferentially disposed around the axis, the inner end of the sleeve being arranged as an abutment flange, the flange being connected to the braking system of the aircraft; as well as A low-friction / wear surface is circumferentially disposed on and surrounds the inner surface of the sleeve, wherein the low-friction / wear surface includes a sacrificial ring formed of a composite material, and the low-friction / wear surface abuts against the shaft. The sleeve extends axially along an axis parallel to the shaft, and extends along a length of the shaft from the end opposite to the flange toward the shaft. The sleeve includes a first portion, which is radially aligned with a wheel bearing mounted to the sleeve and the shaft. The first portion extends through the wheel bearing and extends between the wheel bearings. The sleeve includes a second portion that extends from the first portion toward the flange along the axis. The sleeve is continuous between the first part and the second part. The second portion does not support external loads applied directly to it in a direction extending radially from the axis, and The sacrificial ring is located on the second portion of the sleeve, and the sacrificial ring is spaced apart from the first portion.

2. The aircraft landing gear shaft assembly according to claim 1, wherein, The composite material comprises fibers in a polymer matrix.

3. The aircraft landing gear shaft assembly according to claim 2, wherein, The polymer includes polytetrafluoroethylene.

4. The aircraft landing gear shaft assembly according to claim 2, wherein, The fibers include the following options: glass; carbon; Kevlar; basalt; polytetrafluoroethylene; cotton; wood and / or paper.

5. The aircraft landing gear shaft assembly according to claim 1, wherein, The low-friction wear surface is higher than the inner surface.

6. The aircraft landing gear shaft assembly according to any of the preceding claims, comprising a plurality of low-friction surfaces, each of the plurality of low-friction surfaces comprising a composite material ring on a different corresponding portion of the surface of the sleeve.

7. A method for manufacturing a shaft assembly of an aircraft landing gear, the method comprising: Sacrificial rings are formed from composite materials; The sacrificial ring is attached to the inner surface of the sleeve, wherein the sacrificial ring is formed of a composite material and forms a low-friction wear surface that abuts the shaft; Provide the shaft for the shaft assembly of the aircraft landing gear; and Position the sleeve circumferentially around the shaft such that the sacrificial ring abuts against the annular surface of the shaft; The sleeve extends axially along an axis parallel to the shaft and extends along the length of the shaft away from the flange. The inner end of the sleeve is arranged to abut against the flange, which is connected to the aircraft's braking system. The wheel bearing is mounted on the first part of the sleeve, such that the wheel bearing is mounted to the sleeve and the shaft. The sleeve includes a second portion that extends from the first portion toward the flange along the axis. The sleeve extends continuously in the first portion and the second portion. The second part does not support external loads applied directly to it by the wheel bearing in a direction extending radially from the shaft, and The sacrificial ring is located on the second portion of the sleeve, and the sacrificial ring is spaced apart from the first portion.

8. The method according to claim 7, wherein, The step of forming the low-friction wear surface includes making a sacrificial ring of composite material from fibers in a polymer matrix.

9. The method according to claim 8, wherein, The steps of manufacturing the sacrificial ring of the composite material include manufacturing a fiber preform and then introducing it into the polymer matrix.

10. The method according to claim 7, 8 or 9, wherein, The step of incorporating the low-friction wear surface includes in-situ curing the low-friction wear surface on the surface of the sleeve.

11. The method according to any one of claims 7 to 9, further comprising the step of machining the low-friction wear surface to a predetermined size.

12. A shaft assembly for an aircraft landing gear, comprising: A shaft with an axis; A sleeve, the sleeve being disposed circumferentially around the axis; as well as A sacrificial ring, which is formed of a composite material and located on the inner surface of the sleeve, and forms a low-friction wear surface abutting the shaft; The sleeve extends parallel to the axis of the shaft and extends along the length of the shaft between a flange of the shaft and a nut located at the end of the shaft, the flange being configured to connect to the aircraft's braking system. The sleeve includes a first portion that is radially aligned with a wheel bearing mounted to the sleeve and the shaft, and the first portion extends between the wheel bearing. The sleeve includes a second portion that extends axially between the first portion and the flange. The sleeve extends continuously in the first portion and the second portion. The second portion does not support external loads applied directly to it in a direction extending radially from the axis, and The sacrificial ring is located on the second portion of the sleeve, and the sacrificial ring is spaced apart from the first portion along the axis of the shaft.

13. The aircraft landing gear shaft assembly according to claim 12, wherein, The coefficient of friction between the low-friction wear surface and the shaft is less than the coefficient of friction between the inner surface of the sleeve and the shaft.

14. The shaft assembly of the aircraft landing gear according to claim 13, wherein, The coefficient of friction between the low-friction wear surface and the shaft is less than 0.4 µ.

15. A landing gear assembly for an aircraft, comprising a shaft assembly of the aircraft landing gear according to any one of claims 12 to 14.

16. A landing gear assembly for an aircraft, comprising a pair of columns supported by a shaft assembly of the aircraft landing gear according to any one of claims 12 to 14.

17. The landing gear assembly of an aircraft according to claim 15 or 16, wherein the sleeve is arranged such that a low-friction wear surface is located at the end portion of the sleeve adjacent to a portion of the braking system.

18. An aircraft comprising at least one landing gear assembly of an aircraft according to any one of claims 15 to 17.

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