A manufacturing process for folding hinges

Abstract

This invention relates to the technical field of low-altitude aircraft, specifically disclosing a processing technology for a folding hinge. The process includes the following steps: Step 1: After processing all hinge components except for the first pin hole, assemble them in their final state to obtain a pre-assembled hinge, and apply a preload force P to the pre-assembled hinge; then, locate the position of the first pin hole according to the design drawings, and machine a small hole at the first pin hole position, making the diameter of the small hole smaller than the diameter of the first pin hole; Step 2: Drill a second hole, first applying a force to the moving end of the hinge, the force being a working load ±n, causing the hinge to undergo the expected deformation, and then enlarging the small hole until the hole diameter and the center of the hole meet the requirements of the first pin hole, obtaining the final first pin hole; The processing technology for the folding hinge in this solution solves the problem of misalignment of the pin holes on the stationary and moving parts due to hinge deformation after loading.

Description

Technical Field

[0001] This invention relates to the technical field of low-altitude aircraft, specifically to a processing technology for folding hinges. Background Technology

[0002] Low-altitude aircraft refer to aircraft that fly at an altitude of less than 1,000 meters, mainly including flying cars, air-to-ground integrated aircraft, and drones. Low-altitude aircraft mainly rely on the rotation of their rotors to provide lift and propulsion for levitation in the air, making rotors an essential component of low-altitude aircraft.

[0003] Taking flying cars as an example, the rotors of traditional low-altitude aircraft cannot be folded. However, for relatively large flying cars, the rotors are large. When flying cars are driving on the ground, the rotors will affect the car's power and, due to their large size, may cause collisions with vehicles or facilities on the road, thus affecting driving safety. Therefore, there are currently designs that fold the arms related to the rotors, so that when flying cars are driving on the ground, the arms can be folded and retracted to maintain a smaller size.

[0004] The folding hinge is the core component of the folding arm. The smoothness of the arm's folding and unfolding, as well as its ability to maintain structural reliability under the complex stresses such as centrifugal force, torque, and starting load that the flying car experiences during flight, are key factors in whether the folding arm can be applied.

[0005] The current hinge consists of a stationary part and a moving part, which are connected by a pin. In order to position the arm after it is folded and unfolded, the stationary part of the hinge has a second pin hole, and the moving part has a first pin hole. After the arm is folded or unfolded, a rod-shaped locking structure is inserted into the corresponding pin holes on the stationary part and the moving part. By locking the stationary part and the moving part, the arm is locked, keeping the arm in the folded or unfolded state.

[0006] However, existing hinges use a "bar forging + integral milling" process, with a forging allowance of 5mm or more. Subsequent milling removes a significant portion of the material. However, residual stress is easily generated during the cutting process, leading to hinge deformation. Hinge deformation results in poor hinge structure stability, affecting the safety and stability of use. It also leads to insufficient fit between stationary and moving parts after installation, resulting in the inability to lock the moving and stationary parts. Summary of the Invention

[0007] The present invention aims to provide a processing technology for folding hinges to solve the problem that hinges are prone to deformation, resulting in misalignment of the pin holes on the stationary and moving parts.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a processing technology for folding hinges, comprising the following steps: Step 1: After all hinge components except for pin hole 1 have been machined, they are assembled in their final state to obtain a pre-assembled hinge. A preload force P is then applied to the pre-assembled hinge. Next, the position of pin hole 1 is located according to the design drawings, and a small hole is machined at the position of pin hole 1, so that the diameter of the small hole is smaller than the diameter of pin hole 1. Step 2: Second drilling. First, apply a force to the moving end of the hinge. The force is the working load ±n, so that the hinge produces the expected deformation. Then, enlarge the small hole until the hole diameter and the center of the hole diameter meet the requirements of the first pin hole, and obtain the final first pin hole.

[0009] Where n is a constant greater than or equal to 0, and the value of n is determined based on the material of the pre-assembled hinge and the precision requirements for the assembly of moving and stationary parts.

[0010] The beneficial effects of this plan are: 1. Due to the weight of the connected arms, motors, and other structures, the hinges are subjected to stress during normal use, especially under heavy loads. These forces are significant and can cause deformation of the moving parts of the hinge, resulting in misalignment between the pin holes on the stationary and moving parts. This solution addresses this by applying a preload to control the hinge deformation. Under this preload, the small holes machined are then enlarged to create a pin hole (the first pin hole) that aligns with the pin hole (the second pin hole) on the stationary part of the hinge during use, ensuring accurate positioning of the arm after folding and unfolding. Testing revealed that the resulting moving part exhibits better coaxiality with the stationary part of the unfolded arm during use, resulting in smaller clearances between adjacent hinge components and improved flight balance.

[0011] To prevent hinge deformation from causing a mismatch between stationary and moving parts, current hinges typically use stronger materials. However, these materials often have a higher density. While the density of the material doesn't have an adverse effect in ordinary automobiles or other applications, actual testing has shown that when such hinges are used in flying cars, hinges of the same size have a greater weight, resulting in an excessively large overall mass of the flying car. Compared to cars on the ground, the overall mass of a flying car has a greater impact on energy consumption and the load on the power motor when flying at low altitudes.

[0012] When manufacturing hinges using the processing technology described in this solution, the hinges do not require the use of higher-density, higher-strength materials, reducing material and processing costs while ensuring that pin holes one and two on the hinge can be aligned when the arm needs to be positioned. This process is simple and facilitates mass production. At the same time, the lighter hinges also improve power response speed and extend the flight time of the flying car.

[0013] Secondly, testing revealed that even with stronger materials and under load, a deviation of at least 0.5mm occurred during the machining of pin hole one. This deviation resulted in poor coaxiality between pin hole one and pin hole two when the moving part was under stress. Using a pin with a diameter close to that of pin hole one meant the pin could not pass through both aligned pin holes one and two simultaneously, necessitating the use of a smaller diameter pin. However, a smaller diameter pin would leave gaps between itself and the sidewalls of pin holes one and two, preventing complete hinge positioning and causing vibration between the moving and stationary parts, affecting the stable flight of the flying car. Meanwhile, higher machining precision requires higher costs and presents greater machining difficulties. The machining process described in this solution has lower precision requirements and better coaxiality between pin holes one and two after machining, allowing the use of a larger diameter pin to position the hinge and prevent hinge vibration.

[0014] 2. The preload applied before the first drilling can offset some of the working tensile stress during subsequent processing, control elastic deformation, reduce the amount of deformation generated, reduce the probability of fatigue crack initiation, reduce fretting slippage, prevent fretting fatigue and corrosion, and thus improve the dynamic stiffness of the folding hinge in the swing / swing direction and extend its service life.

[0015] 3. This solution first determines the position of the first pin hole by drilling a small hole. This allows the position of the first pin hole to be quickly determined based on the position of the small hole after the working load is applied, even if the pre-assembled hinge deforms. Since the diameter of the small hole is smaller than the design diameter of the first pin hole, even if the center of the small hole deviates from the center of the first pin hole due to material deformation caused by applying a force similar to the working load that the pre-assembled hinge bears during operation, the position and direction of the enlargement can be adjusted to ensure that the center of the first pin hole deviates from the center of the small hole, thus guaranteeing that the position of the first pin hole meets the requirements.

[0016] At the same time, the presence of the small hole also provides a basis for the second drilling, making it easier to enlarge the hole from various directions and to use different methods to further reduce the impact of the second drilling on the material.

[0017] Furthermore, step 1 includes numerical simulation, comprising the following steps: Step a: First, the hinge model is established using the finite element method through material parameters. The material parameters include the design parameters of each component of the hinge, the elastic modulus of the material, and the fit clearance between the moving part and the stationary part. Then, the bolt preload and the working load at the moving end are simulated. A suitable preload is selected to reduce the deformation of the pre-assembled hinge after the load is applied.

[0018] Furthermore, numerical simulation includes the following steps: Step b: Calculate the preload P using the following formula (1): (1) Where T is the torsional torque applied to the head of the pressure-applying component or nut, K is the bolt coefficient or torque coefficient, and d is the outer diameter of the pressure-applying component.

[0019] Furthermore, the fit clearance is 0.01mm-0.05mm.

[0020] The beneficial effects of this plan are: Numerical simulation revealed that stress concentration or potential cracking risks at the processing location can be identified in advance. If such risks exist, they can be mitigated by adjusting the preload, resulting in stronger and longer-lasting moving parts. This also eliminates the need for repeated hinge sample processing and multiple disassembly and reassembly adjustments of bolt preload parameters to measure blank deformation, effectively reducing the amount of scrapped blanks. Furthermore, eliminating the need for actual testing after the moving parts are formed reduces testing costs and risks, shortens the hinge process development cycle, and consequently lowers overall production costs and improves production efficiency.

[0021] The numerical simulation in this scheme is combined with the calculation of the preload P. The optimal preload can be obtained through a limited number of adjustments during the simulation process, thereby further improving efficiency.

[0022] Further, in step 2, the pre-assembled hinge is assembled with the tooling for simulating the load, and the working load is applied to the tooling for simulating the load.

[0023] The beneficial effects of this solution are as follows: In terms of process sequence, this solution adopts the method of preloading first and then drilling and enlarging the hole to form the pin hole. Compared with the traditional method of drilling first and then processing, the preloading causes the local yielding and micro-defect closure of the pre-assembled hinge. Subsequently, the reference surface is finely ground, which greatly improves the roundness of the hole compared with the traditional precision, and greatly reduces the positional accuracy (gap) or deformation error, so as to achieve high-precision fit and installation. After testing, the hinge finally processed meets the "zero shim" assembly requirements.

[0024] Secondly, after the aforementioned tooling and hinge are installed, the moving parts are simulated to be directly connected to the hinge, and the components that apply forces to the moving hinge are simulated, taking a flying car as an example, as the arm connected to the moving parts. This solution applies a working load to the arm, so that the working load is transmitted to the moving parts through the connection between the arm and the moving parts. The stress on the moving parts is closer to its actual installation, resulting in better coaxiality between pin hole one and pin hole two after hinge installation.

[0025] Furthermore, the diameter of the small hole is 0.9-0.95 times the diameter of the pin hole.

[0026] The beneficial effects of this solution are as follows: After testing, the above parameters will be limited, which can further improve the coaxiality of pin hole one and pin hole two while retaining sufficient secondary machining allowance. Attached Figure Description

[0027] Figure 1 This is a perspective view of the folding hinge in an embodiment of the present invention; Figure 2 This is a test diagram of deformation and preload of the present invention. Detailed Implementation

[0028] The following detailed description illustrates the specific implementation method: The reference numerals in the accompanying drawings include: stationary part 1, pin hole 2, moving part 3, and pin hole 1.

[0029] Example The implementation examples are basically as follows Figure 1 As shown, a processing technology for folding hinges is used to process the following folding hinges: the folding hinge includes a stationary part 1 and a moving part 3, both the stationary part 1 and the moving part 3 are provided with bolt mounting holes and connection holes, the top of the moving part 3 is provided with a first pin hole 4, and the right side of the stationary part 1 is provided with a second pin hole 2.

[0030] The manufacturing process of the folding hinge disclosed in this invention includes the following steps: Step 1: Except for the first pin hole 4, all hinge components, including the second pin hole 2, are processed and then assembled in their final state to obtain a pre-assembled hinge. Then, the force conditions of the stationary part 1 and the moving part 3 during the actual operation of the folding hinge are simulated, and a suitable preload is applied at the force-bearing position. Specifically, the preload in this embodiment is 35000N. Simultaneously, numerical simulation is performed, which includes the following steps: Step a: First, the hinge model is established using the finite element method through material parameters. The material parameters include the design parameters of each component of the hinge, the elastic modulus of the material, and the fit clearance between the moving part 3 and the stationary part 1. Then, the bolt preload and the working load of the moving end are simulated. A suitable preload is selected to reduce the deformation of the pre-assembled hinge after the load is applied. Specifically, the fit clearance in this embodiment is 0.01mm-0.05mm. Step b: Calculate the preload P using the following formula (1): (1) T is the torsional torque applied to the head of the pressure-applying component or nut, K is the bolt coefficient or torque coefficient, and d is the outer diameter of the pressure-applying component. When the pressure-applying component is a bolt, d is the nominal diameter of the bolt. Step a: After applying the preload, measure the actual deformation of the moving part 3. Simultaneously measure the deformation of the moving part 3 while applying the preload, calculate the change in deformation divided by the change in preload, and ensure that this value is less than or equal to 1.2 × 10⁻⁶. -5 Furthermore, the smaller the value, the higher the accuracy. In actual implementation, the corresponding value can be selected according to the accuracy requirements. In this embodiment, the unit of preload is N and the unit of deformation is mm in the calculation of the ratio of deformation to preload change. In actual implementation, if the units of the measured data are not N and mm, the unit of preload should be converted to N and the unit of deformation to mm first to obtain the deformation-preload test result. Please refer to [reference needed]. Figure 2 The preload should be selected within a suitable range where the ratio of preload to deformation change gradually decreases. In actual implementation, when high precision is required for pin hole 2 and the pin hole itself, the ratio of preload to deformation change should be within the range of 1.2 × 10⁻⁶. -5 -0, specifically, in this embodiment, the value is 1.2 × 10. -5 The preload P is determined and applied. Then, the position of pin hole 4 is located according to the design drawings, and a small hole is machined at the position of pin hole 4, so that the diameter of the small hole is smaller than the diameter of pin hole 4. Specifically, in this embodiment, the diameter of the small hole is 0.9-0.95 times the diameter of pin hole 4. Step 2: Drill a second hole and assemble the pre-assembled hinge with the tooling simulating the load. Apply the working load to the tooling simulating the load. First, apply a force to the moving end of the hinge moving part 3 to cause the hinge to deform as expected. The force is the working load ± n, where n is a constant greater than or equal to 0. Specifically, the value of n is determined according to the material of the pre-assembled hinge and the accuracy requirements for assembling the moving part 3 and the stationary part 1, ensuring that the pin hole 4 and the pin hole 2 can be aligned when the moving hinge is subjected to the working load; in this embodiment, the value of n is 0. When the stationary part 1 and the moving part 3 are assembled, the position of the first pin hole 4 is opposite to the position of the second pin hole 2. At this time, the position of the first pin hole 4 on the moving part 3 can be determined according to the position of the second pin hole 2 on the stationary part 1 of the hinge. The small hole is then enlarged. When enlarging the hole, the tool passes through the small hole into the moving part 3 and enlarges the hole from the side of the moving part 3 facing the second pin hole 2 until the hole diameter and the center of the hole diameter meet the requirements of the first pin hole 4, thus obtaining the final first pin hole 4. After the pin hole 4 is machined, while maintaining the applied force, other holes such as bolt mounting holes and connection holes are machined on the moving part 3.

[0031] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A processing technology for folding hinges, characterized in that: Includes the following steps: Step 1: After all hinge components except for pin hole 1 have been machined, they are assembled in their final state to obtain a pre-assembled hinge. A preload force P is then applied to the pre-assembled hinge. Next, the position of pin hole 1 is located according to the design drawings, and a small hole is machined at the position of pin hole 1, so that the diameter of the small hole is smaller than the diameter of pin hole 1. Step 2: Second drilling. First, apply a force to the moving end of the hinge. The force is the working load ±n, so that the hinge produces the expected deformation. Then, enlarge the small hole until the hole diameter and the center of the hole diameter meet the requirements of the first pin hole, and obtain the final first pin hole.

2. The processing technology for a folding hinge according to claim 1, characterized in that: Step 1 includes numerical simulation, comprising the following steps: Step a: First, the hinge model is established using the finite element method through material parameters. The material parameters include the design parameters of each component of the hinge, the elastic modulus of the material, and the fit clearance between the moving part and the stationary part. Then, the bolt preload and the working load at the moving end are simulated. A suitable preload is selected to reduce the deformation of the pre-assembled hinge after the load is applied.

3. The processing technology for a folding hinge according to claim 2, characterized in that: Numerical simulation includes the following steps: Step b: Calculate the preload P using the following formula (1): （1） Where T is the torsional torque applied to the head of the pressure-applying component or nut, K is the bolt coefficient or torque coefficient, and d is the outer diameter of the pressure-applying component.

4. The processing technology for a folding hinge according to claim 2, characterized in that: The fit clearance is 0.01mm-0.05mm.

5. The processing technology for a folding hinge according to claim 1, characterized in that: Step 2: Assemble the pre-assembled hinge with the tooling for simulating the load, and apply the working load to the tooling for simulating the load.

6. The processing technology for a folding hinge according to claim 1, characterized in that: The diameter of the small hole is 0.9-0.95 times the diameter of the pin hole.

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