Connecting device for inner half hub and outer half hub in aircraft hub

Abstract

The utility model relates to a connecting device for an inner half hub and an outer half hub in an aircraft hub, which comprises a butt-joint bolt and a self-locking nut which are used for connecting the inner half hub and the outer half hub, and the butt-joint bolt comprises a head wrenching structure, a head supporting flange and a cylindrical polish rod. Smooth transition is achieved between the head supporting flange and the polish rod through a head lower round corner, an external thread is arranged outside the end, away from the head supporting flange, of the polish rod, a head lightening hole is formed in the end face of the end, away from the head supporting flange, of the head wrenching structure, and meanwhile the axis of the polish rod is coaxial with the axis of the head supporting flange and the axis of the external thread. The self-locking nut comprises a supporting end face, a nut wrenching structure, a supporting end internal thread, a closing-up portion and a deformation locking internal thread, and when the butt-joint bolt is screwed with the self-locking nut, the external thread extends out of the end of the deformation locking internal thread. The locking device is high in strength, long in fatigue life and reliable in locking performance, and guarantees operation safety of aircrafts.

Description

Technical Field

[0001] This utility model relates to the field of connection technology in aircraft wheel hubs, specifically a connection device for connecting the inner half of the wheel hub and the outer half of the wheel hub in an aircraft. Background Technology

[0002] With the development of China's aviation industry, aircraft safety and operational performance are receiving increasing attention. The wheel hub of a civil aircraft mainly consists of an inner half-hub and an outer half-hub, which are connected together by multiple sets of bolts and self-locking nuts. As crucial load-bearing components connecting the inner and outer half-hubs, the strength, fatigue life, and locking performance of these bolts and nuts play a vital role in the aircraft's operational safety and economic efficiency. Current technologies are based on the requirements of civil aviation aircraft and require further breakthroughs. Utility Model Content

[0003] To address the aforementioned problems, this utility model provides a connection device for connecting the inner and outer halves of an aircraft wheel hub, characterized by high strength, long fatigue life, and reliable locking performance.

[0004] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: a connecting device for the inner half-hub and the outer half-hub in an aircraft wheel hub, including a mating bolt and a self-locking nut for connecting the inner half-hub and the outer half-hub. The mating bolt includes a head wrench structure, a head support flange and a cylindrical smooth rod arranged in sequence. The head support flange and the smooth rod achieve a smooth transition through a head fillet formed by rolling. The end of the smooth rod away from the head support flange is provided with an external thread. The end face of the head wrench structure away from the head support flange is provided with a head weight reduction hole. At the same time, the axis of the smooth rod is coaxial with the axis of the head support flange and the external thread. The self-locking nut includes a support end face, a nut wrench structure, a support end internal thread, a closing part and a deformable locking internal thread. The support end internal thread matches the external thread. The deformable locking internal thread is located in the closing part and the deformable locking internal thread and the external thread generate a compressive force on the thread mating surface through threaded engagement. When the mating bolt and the self-locking nut are screwed together, the external thread extends out from the end of the deformable locking internal thread.

[0005] Preferably, the head support flange and the head lever structure are transitioned by a conical surface and a cylindrical surface, and the head support flange is a cylindrical surface with the end face facing inwards as a half-hub with the end face diameter being 1.7 times the diameter of the smooth rod.

[0006] Preferably, washers (303) are provided between the end face of the head support flange and the inner half-hub, and between the support end face of the self-locking nut and the outer half-hub.

[0007] Preferably, the head tightening structure is a dodecagonal prism, and the nut tightening structure of the self-locking nut is a hexagonal prism.

[0008] Preferably, the axis of the head weight reduction hole is coaxial with the axis of the head support flange, and the bottom of the head weight reduction hole has a smooth transition rounded corner.

[0009] Preferably, the materials of the butt bolts and self-locking nuts are both hot work die steel, and the surface treatment of the butt bolts and self-locking nuts is cadmium plating passivation.

[0010] Preferably, the mating bolts and self-locking nuts are provided in multiple sets and are equidistantly distributed along the circumferential direction of the hub.

[0011] Preferably, the external thread adopts a low-stress-concentration type of thread with controlled corner radius at the root of the thread.

[0012] Preferably, the constricted portion is formed by three-point compression and flattening deformation of the protruding outer cylindrical surface on the nut tightening structure towards the center.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The mating bolts and self-locking nuts of this utility model have the advantages of high strength, long fatigue life and reliable locking performance, which can provide a guarantee for the safe operation of aircraft, increase the replacement interval of mating bolts and self-locking nuts during use, reduce maintenance and operating costs, and have broad application prospects.

[0015] 2. The tensile test results of the butt bolts (nominal thread diameter of 0.625 inches) of this utility model show an ultimate tensile strength of not less than 1517 MPa. Under fatigue test tensile load cycles (high tensile load 138.8 kN and low tensile load 13.88 kN), the minimum fatigue life of the butt bolts of this utility model is 72,900 cycles. According to the aerospace bolt standard NASM 8906, the minimum fatigue life required for bolts with an ultimate tensile strength of not less than 1517 MPa under the above-mentioned fatigue test tensile load cycles is 65,000 cycles. The fatigue life of the butt bolts of this utility model exceeds the standard requirement by 12%.

[0016] 3. The locking performance of the self-locking nut of this utility model, which mates with the connecting bolt, can meet the requirement that the maximum locking torque does not exceed 34 N·m and the minimum locking torque is not less than 3.6 N·m during 15 installation and removal cycles. According to the Civil Aviation Aircraft Parts Maintenance and Operation Manual, the usable number of installation and removal cycles for a self-locking nut, under the condition of meeting the above maximum and minimum locking torque, is 12. The usable number of installation and removal cycles for the self-locking nut of this utility model exceeds the requirement of the Aircraft Parts Maintenance and Operation Manual by 25%. Attached Figure Description

[0017] Figure 1 This is the front view of the butt bolt of this utility model;

[0018] Figure 2 This is a left view of the butt bolt of this utility model;

[0019] Figure 3 This is a cross-sectional view of the location of the weight reduction hole in the head of the bolt of this utility model;

[0020] Figure 4 This is a front view of the self-locking nut of this utility model;

[0021] Figure 5 This is a half-sectional view of the self-locking nut of this utility model;

[0022] Figure 6 This is a schematic diagram of the installation of this utility model on an aircraft wheel hub. Detailed Implementation

[0023] The following will combine Figure 1-6 The present invention will be described in detail below. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0024] A connecting device for an inner half-hub and an outer half-hub in an aircraft wheel hub includes a mating bolt 100 for connecting the inner half-hub 301 and the outer half-hub 302, and a matching self-locking nut 200. The mating bolt includes a head-tightening structure 101, a head-supporting flange 102, and a cylindrical smooth rod 104 arranged sequentially. The head-supporting flange and the smooth rod achieve a smooth transition through a head fillet 103 formed by rolling. The head fillet 103 has a high surface quality, which helps to reduce stress concentration effect and improve strength. The end of the smooth rod away from the head-supporting flange is provided with an external thread 105. The end face of the head-tightening structure away from the head-supporting flange is provided with a head weight-reducing hole 106. The axis of the head weight-reducing hole is coaxial with the axis of the head-supporting flange, and the head weight-reducing hole... The bottom has a smooth, rounded corner, which reduces weight and avoids stress concentration. The smooth rod is cylindrical, and its axis is coaxial with the axis of the head support flange and the external thread. The smooth rod 104 can pass through the mounting hole on the hub and bear and transmit loads. The self-locking nut includes a support end face 201, a nut tightening structure 202, a support end internal thread 203, a closing part 204, and a deformable locking internal thread 205. The support end internal thread matches the external thread and has a standard specification form that mates with the external thread, ensuring that the two can be smoothly screwed together. The deformable locking internal thread is located in the closing part, and the deformable locking internal thread and the external thread generate extrusion force on the thread mating surface through threaded engagement. When the butt bolt is screwed into the self-locking nut, the external thread extends from the end of the deformable locking internal thread.

[0025] The head support flange and the head wrench structure are connected by a conical and cylindrical surface. When the connecting bolts are installed and working, the cylindrical end face of the head support flange faces the inner half of the hub, and this end face is in contact with the washer 303 on the inner half of the hub. The diameter of the end face is 1.7 times the diameter of the smooth rod. The larger contact area helps to reduce contact stress and improve rigidity. At the same time, the support end face of the self-locking nut is in close contact with the washer 303 on the outer half of the hub when working, and has a certain area to reduce contact stress during operation.

[0026] The head wrench structure is a dodecagonal prism, which can be matched with a wrench with a suitable opening. During installation and disassembly, the twelve contact working surfaces can distribute the wrench pressure and reduce the wear between the wrench structure surface and the wrench. The self-locking nut has a hexagonal prism structure with high structural rigidity, which can withstand a large torque and reduce the risk of thread stripping.

[0027] The materials for the butt bolts and self-locking nuts are all hot work die steel. The yield strength and ultimate tensile strength of the materials are enhanced by the heat treatment process of quenching and tempering, ensuring that the ultimate tensile strength is not less than 1517MPa.

[0028] During operation under load, the external load is converted into tensile loads acting on the mating bolts 100 and self-locking nuts 200 through the inner half-hub 301 and outer half-hub 302. When the aircraft tires touch down, the load distribution on the hub is uneven due to tire deformation caused by pressure. Since multiple sets of mating bolts 100 and self-locking nuts 200 are evenly distributed along the circumference of the hub, the set of mating bolts 100 and self-locking nuts 200 closest to the ground bears a high tensile load, while the set farthest from the ground bears a low tensile load. When the aircraft hub rotates, the tensile force on each set of mating bolts 100 and self-locking nuts 200 changes between high and low tensile loads with each revolution of the hub. According to the fatigue cumulative damage theory, the more revolutions, the greater the fatigue cumulative damage. Due to the notch stress concentration effect, the root of the external thread 105 of the mating bolt 100 is the most dangerous section for fatigue damage. To improve the fatigue life of the external thread 105, the external thread 105 adopts a low stress concentration type of thread (such as UNJF type thread or MJ type thread) that controls the radius of the fillet at the root of the thread, and rolls the entire thread tooth to maintain the integrity of the material flow line at the root of the thread and have a high surface finish, thereby offsetting the internal tensile stress caused by heat treatment and machining.

[0029] The surface treatment of the butt bolt 100 and the self-locking nut 200 is cadmium plating passivation, and the color is a rainbow-colored golden yellow. Under seawater and salt spray conditions, it is an anodic coating on the base material steel, which protects the base metal from corrosion through electrochemical action.

[0030] The constriction portion 204 is manufactured by a three-point compression flattening deformation method on the protruding outer cylindrical surface of the nut tightening structure 202 towards the center. Before the constriction portion 204 is flattened, the internal thread inside the constriction portion 204 has the same standard specification size and shape as the internal thread 203 of the support end. After the constriction portion 204 is flattened, the internal thread inside the constriction portion 204 undergoes permanent plastic deformation, changing from a standard specification internal thread to a deformed locking internal thread 205. When the self-locking nut 200 is screwed onto the mating bolt 100, a compressive force can be generated between the deformed locking internal thread 205 and the external thread 105 on the thread mating surface, generating a locking torque that hinders the relative movement of the two due to friction. The diameter and amount of compression deformation of the protruding outer cylindrical surface on the tightening structure 202 are determined by a locking torque test to ensure that the locking torque generated by the flattening deformation is within the required range.

[0031] When installing the mating bolt 100 and self-locking nut 200 on the hub, first pass the smooth rod 104 and external thread 105 through the mounting holes and washer 303 on the inner half hub 301 and outer half hub 302, keeping the end face of the head support flange 102 in contact with the washer 303. The internal thread 203 of the self-locking nut 200 can be easily screwed onto the external thread 105 of the mating bolt 100 using finger torque until the end of the external thread 105 contacts the deformed locking internal thread 205. Screwing stops because the finger torque cannot overcome the locking torque caused by the deformed locking internal thread 205. If the head tightening structure 101 is fixed, the torque can be increased further using a torque wrench until it exceeds the locking torque value. At this point, the external thread 105 compresses the deformed locking internal thread 205, causing it to elastically deform. Under this compressed state, the deformed locking internal thread 205 can continue to rotate relative to the external thread 105 and screw forward. Continue screwing in while maintaining a torque greater than the locking torque, and the external thread 105 will gradually extend from the end of the deformed locking internal thread 205.

[0032] After the support end face 201 of the self-locking nut 200 is in contact with the washer 303 on the hub, the self-locking nut 200 is tightened to the specified torque, so that the mating bolt 100 generates a pre-tightening tension and sufficient clamping force between the inner half of the hub 301 and the outer half of the hub 302, so that they are fastened together to support the tire and bear the ground load of the aircraft. When under load, because the deformable locking internal thread 205 on the self-locking nut 200 is squeezed by the external thread 105 of the mating bolt 100, it still maintains an elastic deformation state. Therefore, the extrusion force and locking torque on the thread mating surfaces of the two are always present, which can effectively prevent relative rotation between the mating bolt 100 and the self-locking nut 200, so as to ensure that the inner half of the hub 301 and the outer half of the hub 302 are in tight contact without separation gap.

[0033] During disassembly, use a torque wrench to overcome the locking torque and unscrew the self-locking nut 200 in the opposite direction to that used during installation. After the deformed locking internal thread 205 separates from the external thread 105, the thread compression and elastic deformation on the deformed locking internal thread 205 disappear, and the closing part 204 also returns to its flattened and deformed state. The self-locking nut 200 can be used again during the next installation and provides locking torque.

[0034] The tensile performance test results and fatigue life test results of the butt bolts (nominal thread diameter of 0.625 inches) in this utility model are shown in Table 1 and Table 2, respectively, and the locking torque test results of the matching self-locking nuts are shown in Table 3.

[0035] Table 1. Tensile property test results of butt bolts

[0036]

[0037]

[0038] Table 2. Fatigue life test results of butt bolts

[0039]

[0040] Table 3. Test results of tightening torque of self-locking nuts

[0041]

[0042] Table 1 shows that the tensile test results for the butt bolts (nominal thread diameter of 0.625 inches) show an ultimate tensile strength of not less than 1517 MPa. Table 2 shows that under fatigue test tensile load cycles (high tensile load 138.8 kN and low tensile load 13.88 kN), the minimum fatigue life of the butt bolts of this patent is 72,900 cycles. According to the aerospace bolt standard NASM 8906, the minimum fatigue life required for bolts with an ultimate tensile strength of not less than 1517 MPa under the above-mentioned fatigue test tensile load cycles is 65,000 cycles. The fatigue life of the butt bolts of this utility model exceeds the standard requirement by 12%.

[0043] Due to the inhomogeneity of the materials, as shown in Table 2, some butt bolts may have a continuous surface but with small defects, such as scratches, which are caused by processing, electroplating, or rolling. For example, No. 01 has more scratches, so its fatigue life test value is only 72,900 cycles. On the other hand, Nos. 02 / 03 / 04 have almost no scratches, so their fatigue life test values ​​reach 120,000 or 130,000 cycles. This proves that the structural composition of our butt bolts can reach at least 72,900 cycles, which far exceeds the fatigue life value of existing butt bolts.

[0044] Table 3 shows that the locking performance of the self-locking nut that mates with the bolts can meet the requirement that the maximum locking torque does not exceed 34 N·m and the minimum locking torque is not less than 3.6 N·m during 15 installation and removal cycles. According to the Civil Aviation Aircraft Parts Maintenance and Operation Manual, the self-locking nut, under the condition of meeting the above maximum and minimum locking torque, is required to have 12 usable installation and removal cycles. The self-locking nut of this patent exceeds the requirement of the aircraft parts maintenance and operation manual by 25% in terms of the number of usable installation and removal cycles.

[0045] Therefore, the mating bolts and self-locking nuts used in aircraft wheel hubs have the advantages of high strength, long fatigue life, and reliable locking performance, which can ensure the safe operation of aircraft, increase the replacement interval of mating bolts and self-locking nuts during use, reduce maintenance and operating costs, and have broad application prospects.

[0046] The technical solutions provided by the embodiments of this utility model have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of this utility model. The description of the above embodiments is only for helping to understand the principles of the embodiments of this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub, characterized in that: The assembly includes a mating bolt (100) and a self-locking nut (200) for connecting the inner half-hub (301) and the outer half-hub (302). The mating bolt includes a head-tightening structure (101), a head-supporting flange (102), and a cylindrical smooth rod (104) arranged sequentially. The head-supporting flange and the smooth rod achieve a smooth transition through a head fillet (103) formed by rolling. The end of the smooth rod away from the head-supporting flange is provided with an external thread (105). The end face of the head-tightening structure away from the head-supporting flange is provided with a head weight-reducing hole (106). Meanwhile, the axis of the light rod is coaxial with the axis of the head support flange and the external thread. The self-locking nut includes a support end face (201), a nut tightening structure (202), a support end internal thread (203), a closing part (204), and a deformable locking internal thread (205). The support end internal thread matches the external thread. The deformable locking internal thread is located in the closing part, and the deformable locking internal thread and the external thread generate extrusion force on the thread mating surface through threaded engagement. When the mating bolt is screwed into the self-locking nut, the external thread extends from the end of the deformable locking internal thread.

2. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The head support flange and the head lever structure are connected by a conical surface and a cylindrical surface. The head support flange is a cylindrical surface with the end face facing inwards as a half-hub, and the end face diameter is 1.7 times the diameter of the smooth rod.

3. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: Washers (303) are provided between the end face of the head support flange and the inner half-hub, and between the support end face of the self-locking nut and the outer half-hub.

4. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The head tightening structure is a dodecagonal prism, and the nut tightening structure of the self-locking nut is a hexagonal prism.

5. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The axis of the head weight reduction hole is coaxial with the axis of the head support flange, and the bottom of the head weight reduction hole has a smooth transition rounded corner.

6. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The materials of the connecting bolts and self-locking nuts are both hot work die steel, and the surface treatment of the connecting bolts and self-locking nuts is cadmium plating passivation.

7. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The connecting bolts and self-locking nuts are arranged in multiple sets and are equidistantly distributed along the circumference of the hub.

8. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The external thread adopts a low-stress-concentration type of thread with controlled radius of radius at the root of the thread.

9. The connecting device for the inner half-hub and outer half-hub in an aircraft wheel hub according to claim 1, characterized in that: The closing part is formed by three-point compression and flattening deformation of the protruding outer cylindrical surface on the nut tightening structure towards the center.

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